The crystal structure of Na4(UO2)(CO3)3

and its relationship to schrIcircckingerite

YAPING LI S V KRIVOVICHEV AND P C BURNS

Department of Civil Engineering and Geological Sciences University of Notre Dame 156 Fitzpatrick Notre DameIndiana 46556-0767 USA

ABSTR ACT

Crystals of the compound Na4(UO2)(CO3)3 have been synthesized and the structure has been solved Itis trigonal with a = 93417(6) c = 12824(1) AEcirc V = 9692(1) AEcirc 3 space group P3c1 and Z = 4 Thestructure was refined on the basis of F2 (wR2 = 42) for all unique data collected using Mo-Ka X-radiation and a CCD-based detector The final R1 was 20 calculated for 534 unique observed (Fo 54sF) reflections and the goodness-of-fit (S) was 091 The structure contains a uranyl tricarbonatecluster composed of a uranyl hexagonal bipyramid that shares three equatorial edges with CO3

triangles The uranyl tricarbonate clusters are connected through NaO6 and NaO5 polyhedra forming aheteropolyhedral framework structure This compound may be related to a uranyl carbonate phase withthe same composition which has been reported as an alteration phase on the surface of Chernobyllsquolavarsquo and as a mineral in the Jachymov ore district Czech Republic

KEY WORDS uranyl carbonate sodium uranyl carbonate crystal structure nuclear waste

Introduction

MORE than 25 uranyl carbonate minerals areknown (Mandarino 1999) and actinide-carbonatecomplexes are important over a wide variety ofenvironmental conditions (Clark et al 1995) Thecrystal structures of eight uranyl carbonateminerals have been reported On the basis of thepolymerization of cation polyhedra of higherbond valence uranyl carbonates have beengrouped into those containing in nite sheets andthose with an isolated uranyl tricarbonate cluster(Burns 1999) The structures have been solvedfor liebigite Ca2[(UO2)(CO3)3](H2O)11 (Mereiter1982) schrockingerite NaCa3[(UO2)(CO3)3](SO4)F(H2O)10 (Mereiter 1986a) swartziteCaMg[(UO2)(CO3)3](H2O)12 (Mereiter 1986b)andersonite Na2Ca[(UO2)(CO3)3 ](H2O)5 ](Mereiter 1986c) bayleyite Mg2[(UO2)(CO3)3](H2O)18 (Mayer and Mereiter 1986) roubaultite

[Cu2(UO2)3(CO3)2O2(OH)2](H2O)4 (Ginderowand Cesbron 1985) rutherfordine [(UO2)(CO3)](F inch e t a l 1999 ) and bi j voe t i te [M8(UO2)16O8(OH)8(H2O)25](H2O)14 M = REEY (Li et al 2000) Of these roubaultiterutherfordine and bijvoetite each contain sheetsof polyhedra whereas the others contain theuranyl tricarbonate cluster

There are several reports of the compoundNa4(UO2)(CO3)3 in the literature although thestructure has not been published Douglass (1956)synthesized Na4(UO2)(CO3)3 and provided X-raypowder diffraction (XRD) data An unnamedmineral with composition Na4(UO2)(CO3)3 wasreported from the Jachymov ore district where itoccurs as part of the secondary uranyl mineralassemblage (Ondrus et al 1997) A compound ofthe same composition was also reported as analteration phase on Chernobyl lsquolavarsquo (Burakov etal 1999) Recently a mineral with the composi-tion Na4(UO2)(CO3)3 was approved by theCommission on New Minerals and New MineralNames of the International MineralogicalAssociation (Grice and Ferraris 2000) butdetailed information is still unavailable Table 1

2001 The Mineralogical Society

E-mail pburnsndedu

Mineralogical Magazine April 2001 Vol 65(2) pp 297ndash304

TA

BL

E1

Cry

stal

logr

aphi

cin

form

atio

nre

port

edfo

rN

a 4(U

O2)(

CO

3) 3

Sou

rces

Uni

tce

lla

(AEcirc)

b(AEcirc

)c

(AEcirc)

a(8

)b

(8)

g(8

)R

efs

Dou

glas

str

igon

al9

32(1

)12

80(

1)[1

]U

nnam

edm

iner

alfr

omC

zech

tric

lini

c16

468

(2)

275

78(3

)5

222(

2)94

155

(2)

100

58(1

)12

125

(1)

[2]

hexa

gona

l18

621

(3)

128

01(4

)[2

]U

nnam

edm

iner

altr

icli

nic

928

09

295

128

6490

293

911

2411

954

8[3

]C

urre

ntw

ork

trig

onal

934

17(6

)12

824

(1)

[1]

Dou

glas

s(1

956)

[2

]O

ndru

set

al

(199

7)

[3]

Gri

cean

dFe

rrar

is(2

000)

298

YAPING LI ETAL

presents a summary of crystallographic informa-tion reported for compounds with the compositionNa4(UO2)(CO3)3 We have grown a single crystalof Na4(UO2)(CO3)3 using hydrothermal techni-ques and report the structure here

Experimental

Crystal synthesisCrystals of Na4(UO2)(CO3)3 were synthesized byhydrothermal reaction of 4 ml of a 02 M solutionof uranyl acetate with 017 g of sodium carbonateThe solution was heated to 2208C in a Te on-lined Parr bomb for 2 weeks Yellowish anhedralcrystals were recovered by ltration washed withde-ionized water and dried in air

Single-crystal XRD

A single crystal of Na4(UO2)(CO3)3 with dimen-sions 01060106010 mm was selected andmounted on a glass bre and diffraction datawere collected using a Bruker 1K SMART CCDdiffractometer by using Mo-Ka X-radiation and acrystal-to-detector distance of 50 cm More thana hemisphere of 3-dimensional data was collectedusing frame widths of 038 in o with 10 s spentcounting per frame The unit-cell parameters(Table 2) were re ned from 2210 re ectionsusing least-squares techniques The data wereintegrated and corrected for Lorentz polarizationand background effects using the Bruker programSAINT A semi-empirical absorption correctionwas applied on the basis of equivalent re ectionsby modelling the crystal as an ellipsoid thecorrection reduced Rint of 1646 intense re ectionsfrom 49 to 41 A total of 5555 re ections were

measured of which 804 re ections were uniquewith 534 classed as observed (Fo 5 4sF)

Structure solution and refinement

The Bruker SHELXTL Version 5 system ofprograms was used for the determination andre nement of the crystal structure The structurewas solved by direct methods in space group P3c1and was re ned on the basis of F2 for all uniquedata The nal model included all atomic-positional parameters anisotropic-displacementparameters for all atoms and a re nableweighting scheme of the structure factors There nement converged to a wR2 of 42 for alldata an R1 of 20 calculated for the 534 uniqueobserved (Fo5 4sF) re ections and a goodness-of- t (S) of 091 for all data The nal atomiccoordinates and anisotropic-displacement para-meters are given in Table 3 with selectedinteratomic distances given in Table 4 and abond-valence analysis given in Table 5 Observedand calculated structure factors have beendeposited with the Principal Edi tor ofMineralogical Magazine and are available uponrequest

Discussion

Cation coordinationThe structure of Na4(UO2)(CO3)3 contains asingle symmetrically unique U6+ cation whichis part of an approximately linear (UO2)

2+ uranylion (designated Ur) with an average U OUr bondlength of 181 AEcirc (Table 1) The uranyl ion isfurther coordinated by six O atoms that arearranged at the equatorial (designated eq)

TABLE 2 Crystallographic information for Na4(UO2)(CO3)3

a (AEcirc ) 93417(6) Crystal size (mm) 01060106010c (AEcirc ) 12824(1) Total ref 5555V (AEcirc 3) 9692(1) Unique ref 804Space group P3c1 Rint () 535F(000) 968 Unique FO54sF 534m (mm 1) 16986 Final wR2 () 42Dcalc (gcm3) 3715 Final R1 () 20

S 091Unit-cell contents 4[Na4(UO2)(CO3)3]

R1 = S(|Fo| |Fc|) S |Fo|S = [Sw(|Fo Fc)

2(m n)]12 for m = 804 observations and n = 60 parametersw = 1[s2(FO

2) + (002176P)2] P = (max(FO20) + 26FC

2)3

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

299

positions of a hexagonal bipyramid The averageU6+ Oeq bond length is 241 AEcirc (Table 4) whichcompares well with the average [8]U Oeq bondlength of 247(12) AEcirc derived from numerouswell-re ned structures (Burns et al 1997) Thestructure contains one symmetrically unique C4+

cation in the usual triangular coordination withan average C O bond length of 128 AEcirc (Table 4)

There are three symmetrically distinct Nacations in the structure Na1 and Na2 areoctahedrally coordinated by O atoms with anaverage Na1 O bond length of 2501(3) AEcirc and an

average Na2 O bond length of 2444(3) AEcirc TheNa3 cation is coordinated by ve anions with anaverage Na3 O bond length of 2398 AEcirc

Structural connectivity

As is the case with other known uranyl carbonateswith UC ratios of 13 the structure ofNa4(UO2)(CO3)3 contains the uranyl tricarbonatecluster shown in Fig 1a The cluster contains oneUrO6 hexagonal bipyramid that shares three of itsequatorial edges with CO3 triangles As for all

TABLE 3 Atomic coordinates (6104) and displacement parameters (AEcirc 26103) for Na4(UO2)(CO3)3

x y z U(eq) U11 U22 U33 U23 U13 U12

U1 6667 3333 1303(1) 11(1) 10(1) 10(1) 13(1) 0 0 5(1)Na1 0 0 2500 23(1) 22(1) 22(1) 24(2) 0 0 11(1)Na2 0 0 0 22(1) 23(1) 23(1) 20(2) 0 0 11(1)Na3 8769(3) 3076(3) 3764(2) 27(1) 13(1) 16(1) 49(1) 5(1) 1(1) 6(1)O1 6667 3333 2718(4) 20(1) 22(2) 22(2) 17(3) 0 0 11(1)O2 6667 3333 ndash106(4) 23(1) 30(2) 30(2) 9(3) 0 0 15(1)O3 9651(4) 7833(4) 3784(3) 21(1) 15(2) 19(2) 33(2) ndash3(2) ndash2(2) 12(2)O4 460(4) 5959(5) 3817(3) 23(1) 10(2) 10(2) 49(3) 6(2) 6(2) 5(2)O5 1471(4) 3765(5) 3563(3) 26(1) 12(2) 15(2) 55(3) ndash2(2) 0(2) 10(2)C1 733(7) 7444(7) 3723(4) 17(1) 11(3) 13(3) 22(3) ndash1(2) ndash4(2) 2(2)

U(eq) is de ned as one third of the trace of the orthogonalized Uij tensor

TABLE 4 Bond lengths (AEcirc ) and angles (8) for Na4(UO2)(CO3)3

U1 O2 1807(5) Na1 O3adefgh 2501(3)66U1 O1 1814(5)U1 O5abc 2385(4)63 Na2 O3hkaelm 2444(3)66U1 O4abc 2427(3)63U1 Oeqgt 241 Na3 O5n 2286(4)O2 U1 O1 180 Na3 O3i 2323(4)

Na3 O4n 2345(4)C1 O3j 1236(7) Na3 O1 2488(3)C1 O5f 1310(7) Na3 O2o 2547(4)C1 O4 1284(6) ltNa3 Ogt 2398ltC1 Ogt 128

O3j C1 O4 1242(5)O3j C1 O5f 1226(5)O4 C1 O5f 1132(5)ltO C1 Ogt 120

a = x + 1 x + y z + Yacute b = y x z + Yacute c = x y + 1 y + 1 z + Yacute d = y +1 x y z e =y 1 x 1 z + Yacute f = x + y x +1 z g = x 1 y 1 z h = x y y +1 z + Yacute i = x + y +1 x + 1 z j = x 1 y z k = x + y y 1 z Yacute l = x 1 x y z Yacute m = y + 1 x + 1 zYacute n = x + 1 y z o = y + 1 x + 1 z + Yacute

300

YAPING LI ETAL

known structures that contain the uranyl tricarbo-nate cluster these clusters are not directly linkedbut are connected through bonds to lower-valencecations Burns et al (1996) and Burns (1999)therefore grouped these structures with those thatcontain isolated clusters of polyhedra of higherbond-valence

Three symmetrically related Na3O5 polyhedrashare a common edge resulting in a trimer ofcomposition Na3O11 (Fig 1b) Each trimer islinked to three uranyl tricarbonate clusters bysharing equatorial edges of UrO6 hexagonalbipyramids with Na3O5 polyhedra resulting in aheteropolyhedral sheet that is parallel to (001)(Fig 1c) Additional linkages within the sheet areprovided by the sharing of a vertex of the Na3O5

polyhedron with a CO3 triangle Adjacent sheetsare connected along [001] vertices common to allthree Na3O5 polyhedra in the Na3O11 trimer ofone layer correspond to uranyl ion O atoms ofadjacent offset sheets (Fig 1d) The Na1O6 andNa2O6 octahedra share faces resulting in chainsof octahedra that extend along [001] (Fig 1e)Each octahedral vertex is shared with a CO3

triangle and a Na3O5 polyhedron (Fig 1fg)

Related structures with UC = 13

The structures of uranyl carbonate minerals arereviewed and illustrated in Burns (1999) Ofthese the structure of Na4(UO2)(CO3)3 is mostclosely related to that of schrockingeriteNaCa3[(UO2)(CO3)3](SO4)F(H2O)10 whichcontains a heteropolyhedral layer that is similarto the layer in Na4(UO2)(CO3)3 (Mereiter 1986a)

In schrockingerite three symmetrically uniqueCaf7 polyhedra (f unspecied ligand) link bysharing three vertices to form a trimer of

composition Ca3f18 This trimer differs from theNa3O11 trimer in Na4(UO2)(CO3)3 in the coordi-nation of the cations and in the mode ofconnection of the polyhedra shared vertices inCa3f18 in contrast to a shared edge in Na3O11However the way that these trimers are linkedwith uranyl tricarbonate clusters to form hetero-polyhedral sheets is similar in the two structures(Figs 1c 2a) In schrockingerite the sheets arelinked to SO4 tetrahedra on one side and adjacentsheets are connected through hydrogen bonds toH2O groups in the interlayers (Fig 2b) Note thatthe structure of schrockingerite is triclinic but hasa pseudo-trigonal unit cell with parameters a =9634 b = 9635 c = 14391 AEcirc a = 9141 b =9233 g = 12026(8)

The XRD patterns were reported for twopolymorphs of Na4(UO2)(CO3)3 in the PowderDiffraction File (International Center forDiffraction Data) The calculated XRD patternfor Na4(UO2)(CO3)3 agrees well with PDF11-0081 drawn from the work of Douglass(1956) but is signi cantly different from 13-0038 suggesting that the compound we studied isidentical to that prepared by Douglass (1956)

Na4(UO2)(CO3)3 from the Czech Republic and Chernobyl

A sodium uranyl carbonate mineral with thecomposition Na4(UO2)(CO3)3 was found at theJachymov ore district Czech Public (Ondrus etal 1997) but the structure has not been reportedand a complete description of the mineral has notyet appeared Based on powder diffraction databoth triclinic and trigonal unit cells (Table 1)were given for the mineral (Ondrus et al 1997)it was not possible to index all re ections usingthe cell of Douglass (1956) The material studied

TABLE 5 Bond valence analysis for Na4(UO2)(CO3)3

O1 O2 O3 O4 O5 S

U1 157 159 04763 05163 610Na1 01566 090Na2 01866 108Na3 01663 01363 024 023 027 103C1 154 135 127 416S 205 198 211 205 205

bond-valence parameters for U6+ from Burns et al (1997) and for other cations from Breseand OrsquoKeeffe (1991)

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

301

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

TA

BL

E1

Cry

stal

logr

aphi

cin

form

atio

nre

port

edfo

rN

a 4(U

O2)(

CO

3) 3

Sou

rces

Uni

tce

lla

(AEcirc)

b(AEcirc

)c

(AEcirc)

a(8

)b

(8)

g(8

)R

efs

Dou

glas

str

igon

al9

32(1

)12

80(

1)[1

]U

nnam

edm

iner

alfr

omC

zech

tric

lini

c16

468

(2)

275

78(3

)5

222(

2)94

155

(2)

100

58(1

)12

125

(1)

[2]

hexa

gona

l18

621

(3)

128

01(4

)[2

]U

nnam

edm

iner

altr

icli

nic

928

09

295

128

6490

293

911

2411

954

8[3

]C

urre

ntw

ork

trig

onal

934

17(6

)12

824

(1)

[1]

Dou

glas

s(1

956)

[2

]O

ndru

set

al

(199

7)

[3]

Gri

cean

dFe

rrar

is(2

000)

298

YAPING LI ETAL

presents a summary of crystallographic informa-tion reported for compounds with the compositionNa4(UO2)(CO3)3 We have grown a single crystalof Na4(UO2)(CO3)3 using hydrothermal techni-ques and report the structure here

Experimental

Crystal synthesisCrystals of Na4(UO2)(CO3)3 were synthesized byhydrothermal reaction of 4 ml of a 02 M solutionof uranyl acetate with 017 g of sodium carbonateThe solution was heated to 2208C in a Te on-lined Parr bomb for 2 weeks Yellowish anhedralcrystals were recovered by ltration washed withde-ionized water and dried in air

Single-crystal XRD

A single crystal of Na4(UO2)(CO3)3 with dimen-sions 01060106010 mm was selected andmounted on a glass bre and diffraction datawere collected using a Bruker 1K SMART CCDdiffractometer by using Mo-Ka X-radiation and acrystal-to-detector distance of 50 cm More thana hemisphere of 3-dimensional data was collectedusing frame widths of 038 in o with 10 s spentcounting per frame The unit-cell parameters(Table 2) were re ned from 2210 re ectionsusing least-squares techniques The data wereintegrated and corrected for Lorentz polarizationand background effects using the Bruker programSAINT A semi-empirical absorption correctionwas applied on the basis of equivalent re ectionsby modelling the crystal as an ellipsoid thecorrection reduced Rint of 1646 intense re ectionsfrom 49 to 41 A total of 5555 re ections were

measured of which 804 re ections were uniquewith 534 classed as observed (Fo 5 4sF)

Structure solution and refinement

The Bruker SHELXTL Version 5 system ofprograms was used for the determination andre nement of the crystal structure The structurewas solved by direct methods in space group P3c1and was re ned on the basis of F2 for all uniquedata The nal model included all atomic-positional parameters anisotropic-displacementparameters for all atoms and a re nableweighting scheme of the structure factors There nement converged to a wR2 of 42 for alldata an R1 of 20 calculated for the 534 uniqueobserved (Fo5 4sF) re ections and a goodness-of- t (S) of 091 for all data The nal atomiccoordinates and anisotropic-displacement para-meters are given in Table 3 with selectedinteratomic distances given in Table 4 and abond-valence analysis given in Table 5 Observedand calculated structure factors have beendeposited with the Principal Edi tor ofMineralogical Magazine and are available uponrequest

Discussion

Cation coordinationThe structure of Na4(UO2)(CO3)3 contains asingle symmetrically unique U6+ cation whichis part of an approximately linear (UO2)

2+ uranylion (designated Ur) with an average U OUr bondlength of 181 AEcirc (Table 1) The uranyl ion isfurther coordinated by six O atoms that arearranged at the equatorial (designated eq)

TABLE 2 Crystallographic information for Na4(UO2)(CO3)3

a (AEcirc ) 93417(6) Crystal size (mm) 01060106010c (AEcirc ) 12824(1) Total ref 5555V (AEcirc 3) 9692(1) Unique ref 804Space group P3c1 Rint () 535F(000) 968 Unique FO54sF 534m (mm 1) 16986 Final wR2 () 42Dcalc (gcm3) 3715 Final R1 () 20

S 091Unit-cell contents 4[Na4(UO2)(CO3)3]

R1 = S(|Fo| |Fc|) S |Fo|S = [Sw(|Fo Fc)

2(m n)]12 for m = 804 observations and n = 60 parametersw = 1[s2(FO

2) + (002176P)2] P = (max(FO20) + 26FC

2)3

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

299

positions of a hexagonal bipyramid The averageU6+ Oeq bond length is 241 AEcirc (Table 4) whichcompares well with the average [8]U Oeq bondlength of 247(12) AEcirc derived from numerouswell-re ned structures (Burns et al 1997) Thestructure contains one symmetrically unique C4+

cation in the usual triangular coordination withan average C O bond length of 128 AEcirc (Table 4)

There are three symmetrically distinct Nacations in the structure Na1 and Na2 areoctahedrally coordinated by O atoms with anaverage Na1 O bond length of 2501(3) AEcirc and an

average Na2 O bond length of 2444(3) AEcirc TheNa3 cation is coordinated by ve anions with anaverage Na3 O bond length of 2398 AEcirc

Structural connectivity

As is the case with other known uranyl carbonateswith UC ratios of 13 the structure ofNa4(UO2)(CO3)3 contains the uranyl tricarbonatecluster shown in Fig 1a The cluster contains oneUrO6 hexagonal bipyramid that shares three of itsequatorial edges with CO3 triangles As for all

TABLE 3 Atomic coordinates (6104) and displacement parameters (AEcirc 26103) for Na4(UO2)(CO3)3

x y z U(eq) U11 U22 U33 U23 U13 U12

U1 6667 3333 1303(1) 11(1) 10(1) 10(1) 13(1) 0 0 5(1)Na1 0 0 2500 23(1) 22(1) 22(1) 24(2) 0 0 11(1)Na2 0 0 0 22(1) 23(1) 23(1) 20(2) 0 0 11(1)Na3 8769(3) 3076(3) 3764(2) 27(1) 13(1) 16(1) 49(1) 5(1) 1(1) 6(1)O1 6667 3333 2718(4) 20(1) 22(2) 22(2) 17(3) 0 0 11(1)O2 6667 3333 ndash106(4) 23(1) 30(2) 30(2) 9(3) 0 0 15(1)O3 9651(4) 7833(4) 3784(3) 21(1) 15(2) 19(2) 33(2) ndash3(2) ndash2(2) 12(2)O4 460(4) 5959(5) 3817(3) 23(1) 10(2) 10(2) 49(3) 6(2) 6(2) 5(2)O5 1471(4) 3765(5) 3563(3) 26(1) 12(2) 15(2) 55(3) ndash2(2) 0(2) 10(2)C1 733(7) 7444(7) 3723(4) 17(1) 11(3) 13(3) 22(3) ndash1(2) ndash4(2) 2(2)

U(eq) is de ned as one third of the trace of the orthogonalized Uij tensor

TABLE 4 Bond lengths (AEcirc ) and angles (8) for Na4(UO2)(CO3)3

U1 O2 1807(5) Na1 O3adefgh 2501(3)66U1 O1 1814(5)U1 O5abc 2385(4)63 Na2 O3hkaelm 2444(3)66U1 O4abc 2427(3)63U1 Oeqgt 241 Na3 O5n 2286(4)O2 U1 O1 180 Na3 O3i 2323(4)

Na3 O4n 2345(4)C1 O3j 1236(7) Na3 O1 2488(3)C1 O5f 1310(7) Na3 O2o 2547(4)C1 O4 1284(6) ltNa3 Ogt 2398ltC1 Ogt 128

O3j C1 O4 1242(5)O3j C1 O5f 1226(5)O4 C1 O5f 1132(5)ltO C1 Ogt 120

a = x + 1 x + y z + Yacute b = y x z + Yacute c = x y + 1 y + 1 z + Yacute d = y +1 x y z e =y 1 x 1 z + Yacute f = x + y x +1 z g = x 1 y 1 z h = x y y +1 z + Yacute i = x + y +1 x + 1 z j = x 1 y z k = x + y y 1 z Yacute l = x 1 x y z Yacute m = y + 1 x + 1 zYacute n = x + 1 y z o = y + 1 x + 1 z + Yacute

300

YAPING LI ETAL

known structures that contain the uranyl tricarbo-nate cluster these clusters are not directly linkedbut are connected through bonds to lower-valencecations Burns et al (1996) and Burns (1999)therefore grouped these structures with those thatcontain isolated clusters of polyhedra of higherbond-valence

Three symmetrically related Na3O5 polyhedrashare a common edge resulting in a trimer ofcomposition Na3O11 (Fig 1b) Each trimer islinked to three uranyl tricarbonate clusters bysharing equatorial edges of UrO6 hexagonalbipyramids with Na3O5 polyhedra resulting in aheteropolyhedral sheet that is parallel to (001)(Fig 1c) Additional linkages within the sheet areprovided by the sharing of a vertex of the Na3O5

polyhedron with a CO3 triangle Adjacent sheetsare connected along [001] vertices common to allthree Na3O5 polyhedra in the Na3O11 trimer ofone layer correspond to uranyl ion O atoms ofadjacent offset sheets (Fig 1d) The Na1O6 andNa2O6 octahedra share faces resulting in chainsof octahedra that extend along [001] (Fig 1e)Each octahedral vertex is shared with a CO3

triangle and a Na3O5 polyhedron (Fig 1fg)

Related structures with UC = 13

The structures of uranyl carbonate minerals arereviewed and illustrated in Burns (1999) Ofthese the structure of Na4(UO2)(CO3)3 is mostclosely related to that of schrockingeriteNaCa3[(UO2)(CO3)3](SO4)F(H2O)10 whichcontains a heteropolyhedral layer that is similarto the layer in Na4(UO2)(CO3)3 (Mereiter 1986a)

In schrockingerite three symmetrically uniqueCaf7 polyhedra (f unspecied ligand) link bysharing three vertices to form a trimer of

composition Ca3f18 This trimer differs from theNa3O11 trimer in Na4(UO2)(CO3)3 in the coordi-nation of the cations and in the mode ofconnection of the polyhedra shared vertices inCa3f18 in contrast to a shared edge in Na3O11However the way that these trimers are linkedwith uranyl tricarbonate clusters to form hetero-polyhedral sheets is similar in the two structures(Figs 1c 2a) In schrockingerite the sheets arelinked to SO4 tetrahedra on one side and adjacentsheets are connected through hydrogen bonds toH2O groups in the interlayers (Fig 2b) Note thatthe structure of schrockingerite is triclinic but hasa pseudo-trigonal unit cell with parameters a =9634 b = 9635 c = 14391 AEcirc a = 9141 b =9233 g = 12026(8)

The XRD patterns were reported for twopolymorphs of Na4(UO2)(CO3)3 in the PowderDiffraction File (International Center forDiffraction Data) The calculated XRD patternfor Na4(UO2)(CO3)3 agrees well with PDF11-0081 drawn from the work of Douglass(1956) but is signi cantly different from 13-0038 suggesting that the compound we studied isidentical to that prepared by Douglass (1956)

Na4(UO2)(CO3)3 from the Czech Republic and Chernobyl

A sodium uranyl carbonate mineral with thecomposition Na4(UO2)(CO3)3 was found at theJachymov ore district Czech Public (Ondrus etal 1997) but the structure has not been reportedand a complete description of the mineral has notyet appeared Based on powder diffraction databoth triclinic and trigonal unit cells (Table 1)were given for the mineral (Ondrus et al 1997)it was not possible to index all re ections usingthe cell of Douglass (1956) The material studied

TABLE 5 Bond valence analysis for Na4(UO2)(CO3)3

O1 O2 O3 O4 O5 S

U1 157 159 04763 05163 610Na1 01566 090Na2 01866 108Na3 01663 01363 024 023 027 103C1 154 135 127 416S 205 198 211 205 205

bond-valence parameters for U6+ from Burns et al (1997) and for other cations from Breseand OrsquoKeeffe (1991)

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

301

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

presents a summary of crystallographic informa-tion reported for compounds with the compositionNa4(UO2)(CO3)3 We have grown a single crystalof Na4(UO2)(CO3)3 using hydrothermal techni-ques and report the structure here

Experimental

Crystal synthesisCrystals of Na4(UO2)(CO3)3 were synthesized byhydrothermal reaction of 4 ml of a 02 M solutionof uranyl acetate with 017 g of sodium carbonateThe solution was heated to 2208C in a Te on-lined Parr bomb for 2 weeks Yellowish anhedralcrystals were recovered by ltration washed withde-ionized water and dried in air

Single-crystal XRD

A single crystal of Na4(UO2)(CO3)3 with dimen-sions 01060106010 mm was selected andmounted on a glass bre and diffraction datawere collected using a Bruker 1K SMART CCDdiffractometer by using Mo-Ka X-radiation and acrystal-to-detector distance of 50 cm More thana hemisphere of 3-dimensional data was collectedusing frame widths of 038 in o with 10 s spentcounting per frame The unit-cell parameters(Table 2) were re ned from 2210 re ectionsusing least-squares techniques The data wereintegrated and corrected for Lorentz polarizationand background effects using the Bruker programSAINT A semi-empirical absorption correctionwas applied on the basis of equivalent re ectionsby modelling the crystal as an ellipsoid thecorrection reduced Rint of 1646 intense re ectionsfrom 49 to 41 A total of 5555 re ections were

measured of which 804 re ections were uniquewith 534 classed as observed (Fo 5 4sF)

Structure solution and refinement

The Bruker SHELXTL Version 5 system ofprograms was used for the determination andre nement of the crystal structure The structurewas solved by direct methods in space group P3c1and was re ned on the basis of F2 for all uniquedata The nal model included all atomic-positional parameters anisotropic-displacementparameters for all atoms and a re nableweighting scheme of the structure factors There nement converged to a wR2 of 42 for alldata an R1 of 20 calculated for the 534 uniqueobserved (Fo5 4sF) re ections and a goodness-of- t (S) of 091 for all data The nal atomiccoordinates and anisotropic-displacement para-meters are given in Table 3 with selectedinteratomic distances given in Table 4 and abond-valence analysis given in Table 5 Observedand calculated structure factors have beendeposited with the Principal Edi tor ofMineralogical Magazine and are available uponrequest

Discussion

Cation coordinationThe structure of Na4(UO2)(CO3)3 contains asingle symmetrically unique U6+ cation whichis part of an approximately linear (UO2)

2+ uranylion (designated Ur) with an average U OUr bondlength of 181 AEcirc (Table 1) The uranyl ion isfurther coordinated by six O atoms that arearranged at the equatorial (designated eq)

TABLE 2 Crystallographic information for Na4(UO2)(CO3)3

a (AEcirc ) 93417(6) Crystal size (mm) 01060106010c (AEcirc ) 12824(1) Total ref 5555V (AEcirc 3) 9692(1) Unique ref 804Space group P3c1 Rint () 535F(000) 968 Unique FO54sF 534m (mm 1) 16986 Final wR2 () 42Dcalc (gcm3) 3715 Final R1 () 20

S 091Unit-cell contents 4[Na4(UO2)(CO3)3]

R1 = S(|Fo| |Fc|) S |Fo|S = [Sw(|Fo Fc)

2(m n)]12 for m = 804 observations and n = 60 parametersw = 1[s2(FO

2) + (002176P)2] P = (max(FO20) + 26FC

2)3

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

299

positions of a hexagonal bipyramid The averageU6+ Oeq bond length is 241 AEcirc (Table 4) whichcompares well with the average [8]U Oeq bondlength of 247(12) AEcirc derived from numerouswell-re ned structures (Burns et al 1997) Thestructure contains one symmetrically unique C4+

cation in the usual triangular coordination withan average C O bond length of 128 AEcirc (Table 4)

There are three symmetrically distinct Nacations in the structure Na1 and Na2 areoctahedrally coordinated by O atoms with anaverage Na1 O bond length of 2501(3) AEcirc and an

average Na2 O bond length of 2444(3) AEcirc TheNa3 cation is coordinated by ve anions with anaverage Na3 O bond length of 2398 AEcirc

Structural connectivity

As is the case with other known uranyl carbonateswith UC ratios of 13 the structure ofNa4(UO2)(CO3)3 contains the uranyl tricarbonatecluster shown in Fig 1a The cluster contains oneUrO6 hexagonal bipyramid that shares three of itsequatorial edges with CO3 triangles As for all

TABLE 3 Atomic coordinates (6104) and displacement parameters (AEcirc 26103) for Na4(UO2)(CO3)3

x y z U(eq) U11 U22 U33 U23 U13 U12

U1 6667 3333 1303(1) 11(1) 10(1) 10(1) 13(1) 0 0 5(1)Na1 0 0 2500 23(1) 22(1) 22(1) 24(2) 0 0 11(1)Na2 0 0 0 22(1) 23(1) 23(1) 20(2) 0 0 11(1)Na3 8769(3) 3076(3) 3764(2) 27(1) 13(1) 16(1) 49(1) 5(1) 1(1) 6(1)O1 6667 3333 2718(4) 20(1) 22(2) 22(2) 17(3) 0 0 11(1)O2 6667 3333 ndash106(4) 23(1) 30(2) 30(2) 9(3) 0 0 15(1)O3 9651(4) 7833(4) 3784(3) 21(1) 15(2) 19(2) 33(2) ndash3(2) ndash2(2) 12(2)O4 460(4) 5959(5) 3817(3) 23(1) 10(2) 10(2) 49(3) 6(2) 6(2) 5(2)O5 1471(4) 3765(5) 3563(3) 26(1) 12(2) 15(2) 55(3) ndash2(2) 0(2) 10(2)C1 733(7) 7444(7) 3723(4) 17(1) 11(3) 13(3) 22(3) ndash1(2) ndash4(2) 2(2)

U(eq) is de ned as one third of the trace of the orthogonalized Uij tensor

TABLE 4 Bond lengths (AEcirc ) and angles (8) for Na4(UO2)(CO3)3

U1 O2 1807(5) Na1 O3adefgh 2501(3)66U1 O1 1814(5)U1 O5abc 2385(4)63 Na2 O3hkaelm 2444(3)66U1 O4abc 2427(3)63U1 Oeqgt 241 Na3 O5n 2286(4)O2 U1 O1 180 Na3 O3i 2323(4)

Na3 O4n 2345(4)C1 O3j 1236(7) Na3 O1 2488(3)C1 O5f 1310(7) Na3 O2o 2547(4)C1 O4 1284(6) ltNa3 Ogt 2398ltC1 Ogt 128

O3j C1 O4 1242(5)O3j C1 O5f 1226(5)O4 C1 O5f 1132(5)ltO C1 Ogt 120

a = x + 1 x + y z + Yacute b = y x z + Yacute c = x y + 1 y + 1 z + Yacute d = y +1 x y z e =y 1 x 1 z + Yacute f = x + y x +1 z g = x 1 y 1 z h = x y y +1 z + Yacute i = x + y +1 x + 1 z j = x 1 y z k = x + y y 1 z Yacute l = x 1 x y z Yacute m = y + 1 x + 1 zYacute n = x + 1 y z o = y + 1 x + 1 z + Yacute

300

YAPING LI ETAL

known structures that contain the uranyl tricarbo-nate cluster these clusters are not directly linkedbut are connected through bonds to lower-valencecations Burns et al (1996) and Burns (1999)therefore grouped these structures with those thatcontain isolated clusters of polyhedra of higherbond-valence

Three symmetrically related Na3O5 polyhedrashare a common edge resulting in a trimer ofcomposition Na3O11 (Fig 1b) Each trimer islinked to three uranyl tricarbonate clusters bysharing equatorial edges of UrO6 hexagonalbipyramids with Na3O5 polyhedra resulting in aheteropolyhedral sheet that is parallel to (001)(Fig 1c) Additional linkages within the sheet areprovided by the sharing of a vertex of the Na3O5

polyhedron with a CO3 triangle Adjacent sheetsare connected along [001] vertices common to allthree Na3O5 polyhedra in the Na3O11 trimer ofone layer correspond to uranyl ion O atoms ofadjacent offset sheets (Fig 1d) The Na1O6 andNa2O6 octahedra share faces resulting in chainsof octahedra that extend along [001] (Fig 1e)Each octahedral vertex is shared with a CO3

triangle and a Na3O5 polyhedron (Fig 1fg)

Related structures with UC = 13

The structures of uranyl carbonate minerals arereviewed and illustrated in Burns (1999) Ofthese the structure of Na4(UO2)(CO3)3 is mostclosely related to that of schrockingeriteNaCa3[(UO2)(CO3)3](SO4)F(H2O)10 whichcontains a heteropolyhedral layer that is similarto the layer in Na4(UO2)(CO3)3 (Mereiter 1986a)

In schrockingerite three symmetrically uniqueCaf7 polyhedra (f unspecied ligand) link bysharing three vertices to form a trimer of

composition Ca3f18 This trimer differs from theNa3O11 trimer in Na4(UO2)(CO3)3 in the coordi-nation of the cations and in the mode ofconnection of the polyhedra shared vertices inCa3f18 in contrast to a shared edge in Na3O11However the way that these trimers are linkedwith uranyl tricarbonate clusters to form hetero-polyhedral sheets is similar in the two structures(Figs 1c 2a) In schrockingerite the sheets arelinked to SO4 tetrahedra on one side and adjacentsheets are connected through hydrogen bonds toH2O groups in the interlayers (Fig 2b) Note thatthe structure of schrockingerite is triclinic but hasa pseudo-trigonal unit cell with parameters a =9634 b = 9635 c = 14391 AEcirc a = 9141 b =9233 g = 12026(8)

The XRD patterns were reported for twopolymorphs of Na4(UO2)(CO3)3 in the PowderDiffraction File (International Center forDiffraction Data) The calculated XRD patternfor Na4(UO2)(CO3)3 agrees well with PDF11-0081 drawn from the work of Douglass(1956) but is signi cantly different from 13-0038 suggesting that the compound we studied isidentical to that prepared by Douglass (1956)

Na4(UO2)(CO3)3 from the Czech Republic and Chernobyl

A sodium uranyl carbonate mineral with thecomposition Na4(UO2)(CO3)3 was found at theJachymov ore district Czech Public (Ondrus etal 1997) but the structure has not been reportedand a complete description of the mineral has notyet appeared Based on powder diffraction databoth triclinic and trigonal unit cells (Table 1)were given for the mineral (Ondrus et al 1997)it was not possible to index all re ections usingthe cell of Douglass (1956) The material studied

TABLE 5 Bond valence analysis for Na4(UO2)(CO3)3

O1 O2 O3 O4 O5 S

U1 157 159 04763 05163 610Na1 01566 090Na2 01866 108Na3 01663 01363 024 023 027 103C1 154 135 127 416S 205 198 211 205 205

bond-valence parameters for U6+ from Burns et al (1997) and for other cations from Breseand OrsquoKeeffe (1991)

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

301

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

positions of a hexagonal bipyramid The averageU6+ Oeq bond length is 241 AEcirc (Table 4) whichcompares well with the average [8]U Oeq bondlength of 247(12) AEcirc derived from numerouswell-re ned structures (Burns et al 1997) Thestructure contains one symmetrically unique C4+

cation in the usual triangular coordination withan average C O bond length of 128 AEcirc (Table 4)

There are three symmetrically distinct Nacations in the structure Na1 and Na2 areoctahedrally coordinated by O atoms with anaverage Na1 O bond length of 2501(3) AEcirc and an

average Na2 O bond length of 2444(3) AEcirc TheNa3 cation is coordinated by ve anions with anaverage Na3 O bond length of 2398 AEcirc

Structural connectivity

As is the case with other known uranyl carbonateswith UC ratios of 13 the structure ofNa4(UO2)(CO3)3 contains the uranyl tricarbonatecluster shown in Fig 1a The cluster contains oneUrO6 hexagonal bipyramid that shares three of itsequatorial edges with CO3 triangles As for all

TABLE 3 Atomic coordinates (6104) and displacement parameters (AEcirc 26103) for Na4(UO2)(CO3)3

x y z U(eq) U11 U22 U33 U23 U13 U12

U1 6667 3333 1303(1) 11(1) 10(1) 10(1) 13(1) 0 0 5(1)Na1 0 0 2500 23(1) 22(1) 22(1) 24(2) 0 0 11(1)Na2 0 0 0 22(1) 23(1) 23(1) 20(2) 0 0 11(1)Na3 8769(3) 3076(3) 3764(2) 27(1) 13(1) 16(1) 49(1) 5(1) 1(1) 6(1)O1 6667 3333 2718(4) 20(1) 22(2) 22(2) 17(3) 0 0 11(1)O2 6667 3333 ndash106(4) 23(1) 30(2) 30(2) 9(3) 0 0 15(1)O3 9651(4) 7833(4) 3784(3) 21(1) 15(2) 19(2) 33(2) ndash3(2) ndash2(2) 12(2)O4 460(4) 5959(5) 3817(3) 23(1) 10(2) 10(2) 49(3) 6(2) 6(2) 5(2)O5 1471(4) 3765(5) 3563(3) 26(1) 12(2) 15(2) 55(3) ndash2(2) 0(2) 10(2)C1 733(7) 7444(7) 3723(4) 17(1) 11(3) 13(3) 22(3) ndash1(2) ndash4(2) 2(2)

U(eq) is de ned as one third of the trace of the orthogonalized Uij tensor

TABLE 4 Bond lengths (AEcirc ) and angles (8) for Na4(UO2)(CO3)3

U1 O2 1807(5) Na1 O3adefgh 2501(3)66U1 O1 1814(5)U1 O5abc 2385(4)63 Na2 O3hkaelm 2444(3)66U1 O4abc 2427(3)63U1 Oeqgt 241 Na3 O5n 2286(4)O2 U1 O1 180 Na3 O3i 2323(4)

Na3 O4n 2345(4)C1 O3j 1236(7) Na3 O1 2488(3)C1 O5f 1310(7) Na3 O2o 2547(4)C1 O4 1284(6) ltNa3 Ogt 2398ltC1 Ogt 128

O3j C1 O4 1242(5)O3j C1 O5f 1226(5)O4 C1 O5f 1132(5)ltO C1 Ogt 120

a = x + 1 x + y z + Yacute b = y x z + Yacute c = x y + 1 y + 1 z + Yacute d = y +1 x y z e =y 1 x 1 z + Yacute f = x + y x +1 z g = x 1 y 1 z h = x y y +1 z + Yacute i = x + y +1 x + 1 z j = x 1 y z k = x + y y 1 z Yacute l = x 1 x y z Yacute m = y + 1 x + 1 zYacute n = x + 1 y z o = y + 1 x + 1 z + Yacute

300

YAPING LI ETAL

known structures that contain the uranyl tricarbo-nate cluster these clusters are not directly linkedbut are connected through bonds to lower-valencecations Burns et al (1996) and Burns (1999)therefore grouped these structures with those thatcontain isolated clusters of polyhedra of higherbond-valence

Three symmetrically related Na3O5 polyhedrashare a common edge resulting in a trimer ofcomposition Na3O11 (Fig 1b) Each trimer islinked to three uranyl tricarbonate clusters bysharing equatorial edges of UrO6 hexagonalbipyramids with Na3O5 polyhedra resulting in aheteropolyhedral sheet that is parallel to (001)(Fig 1c) Additional linkages within the sheet areprovided by the sharing of a vertex of the Na3O5

polyhedron with a CO3 triangle Adjacent sheetsare connected along [001] vertices common to allthree Na3O5 polyhedra in the Na3O11 trimer ofone layer correspond to uranyl ion O atoms ofadjacent offset sheets (Fig 1d) The Na1O6 andNa2O6 octahedra share faces resulting in chainsof octahedra that extend along [001] (Fig 1e)Each octahedral vertex is shared with a CO3

triangle and a Na3O5 polyhedron (Fig 1fg)

Related structures with UC = 13

The structures of uranyl carbonate minerals arereviewed and illustrated in Burns (1999) Ofthese the structure of Na4(UO2)(CO3)3 is mostclosely related to that of schrockingeriteNaCa3[(UO2)(CO3)3](SO4)F(H2O)10 whichcontains a heteropolyhedral layer that is similarto the layer in Na4(UO2)(CO3)3 (Mereiter 1986a)

In schrockingerite three symmetrically uniqueCaf7 polyhedra (f unspecied ligand) link bysharing three vertices to form a trimer of

composition Ca3f18 This trimer differs from theNa3O11 trimer in Na4(UO2)(CO3)3 in the coordi-nation of the cations and in the mode ofconnection of the polyhedra shared vertices inCa3f18 in contrast to a shared edge in Na3O11However the way that these trimers are linkedwith uranyl tricarbonate clusters to form hetero-polyhedral sheets is similar in the two structures(Figs 1c 2a) In schrockingerite the sheets arelinked to SO4 tetrahedra on one side and adjacentsheets are connected through hydrogen bonds toH2O groups in the interlayers (Fig 2b) Note thatthe structure of schrockingerite is triclinic but hasa pseudo-trigonal unit cell with parameters a =9634 b = 9635 c = 14391 AEcirc a = 9141 b =9233 g = 12026(8)

The XRD patterns were reported for twopolymorphs of Na4(UO2)(CO3)3 in the PowderDiffraction File (International Center forDiffraction Data) The calculated XRD patternfor Na4(UO2)(CO3)3 agrees well with PDF11-0081 drawn from the work of Douglass(1956) but is signi cantly different from 13-0038 suggesting that the compound we studied isidentical to that prepared by Douglass (1956)

Na4(UO2)(CO3)3 from the Czech Republic and Chernobyl

A sodium uranyl carbonate mineral with thecomposition Na4(UO2)(CO3)3 was found at theJachymov ore district Czech Public (Ondrus etal 1997) but the structure has not been reportedand a complete description of the mineral has notyet appeared Based on powder diffraction databoth triclinic and trigonal unit cells (Table 1)were given for the mineral (Ondrus et al 1997)it was not possible to index all re ections usingthe cell of Douglass (1956) The material studied

TABLE 5 Bond valence analysis for Na4(UO2)(CO3)3

O1 O2 O3 O4 O5 S

U1 157 159 04763 05163 610Na1 01566 090Na2 01866 108Na3 01663 01363 024 023 027 103C1 154 135 127 416S 205 198 211 205 205

bond-valence parameters for U6+ from Burns et al (1997) and for other cations from Breseand OrsquoKeeffe (1991)

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

301

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

known structures that contain the uranyl tricarbo-nate cluster these clusters are not directly linkedbut are connected through bonds to lower-valencecations Burns et al (1996) and Burns (1999)therefore grouped these structures with those thatcontain isolated clusters of polyhedra of higherbond-valence

Three symmetrically related Na3O5 polyhedrashare a common edge resulting in a trimer ofcomposition Na3O11 (Fig 1b) Each trimer islinked to three uranyl tricarbonate clusters bysharing equatorial edges of UrO6 hexagonalbipyramids with Na3O5 polyhedra resulting in aheteropolyhedral sheet that is parallel to (001)(Fig 1c) Additional linkages within the sheet areprovided by the sharing of a vertex of the Na3O5

polyhedron with a CO3 triangle Adjacent sheetsare connected along [001] vertices common to allthree Na3O5 polyhedra in the Na3O11 trimer ofone layer correspond to uranyl ion O atoms ofadjacent offset sheets (Fig 1d) The Na1O6 andNa2O6 octahedra share faces resulting in chainsof octahedra that extend along [001] (Fig 1e)Each octahedral vertex is shared with a CO3

triangle and a Na3O5 polyhedron (Fig 1fg)

Related structures with UC = 13

The structures of uranyl carbonate minerals arereviewed and illustrated in Burns (1999) Ofthese the structure of Na4(UO2)(CO3)3 is mostclosely related to that of schrockingeriteNaCa3[(UO2)(CO3)3](SO4)F(H2O)10 whichcontains a heteropolyhedral layer that is similarto the layer in Na4(UO2)(CO3)3 (Mereiter 1986a)

In schrockingerite three symmetrically uniqueCaf7 polyhedra (f unspecied ligand) link bysharing three vertices to form a trimer of

composition Ca3f18 This trimer differs from theNa3O11 trimer in Na4(UO2)(CO3)3 in the coordi-nation of the cations and in the mode ofconnection of the polyhedra shared vertices inCa3f18 in contrast to a shared edge in Na3O11However the way that these trimers are linkedwith uranyl tricarbonate clusters to form hetero-polyhedral sheets is similar in the two structures(Figs 1c 2a) In schrockingerite the sheets arelinked to SO4 tetrahedra on one side and adjacentsheets are connected through hydrogen bonds toH2O groups in the interlayers (Fig 2b) Note thatthe structure of schrockingerite is triclinic but hasa pseudo-trigonal unit cell with parameters a =9634 b = 9635 c = 14391 AEcirc a = 9141 b =9233 g = 12026(8)

The XRD patterns were reported for twopolymorphs of Na4(UO2)(CO3)3 in the PowderDiffraction File (International Center forDiffraction Data) The calculated XRD patternfor Na4(UO2)(CO3)3 agrees well with PDF11-0081 drawn from the work of Douglass(1956) but is signi cantly different from 13-0038 suggesting that the compound we studied isidentical to that prepared by Douglass (1956)

Na4(UO2)(CO3)3 from the Czech Republic and Chernobyl

A sodium uranyl carbonate mineral with thecomposition Na4(UO2)(CO3)3 was found at theJachymov ore district Czech Public (Ondrus etal 1997) but the structure has not been reportedand a complete description of the mineral has notyet appeared Based on powder diffraction databoth triclinic and trigonal unit cells (Table 1)were given for the mineral (Ondrus et al 1997)it was not possible to index all re ections usingthe cell of Douglass (1956) The material studied

TABLE 5 Bond valence analysis for Na4(UO2)(CO3)3

O1 O2 O3 O4 O5 S

U1 157 159 04763 05163 610Na1 01566 090Na2 01866 108Na3 01663 01363 024 023 027 103C1 154 135 127 416S 205 198 211 205 205

bond-valence parameters for U6+ from Burns et al (1997) and for other cations from Breseand OrsquoKeeffe (1991)

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

301

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

by Ondrus et al (1997) was ne grained It ispossible that some peaks in the diffraction patternare due to impurities The results of our work mayprovide the structure of the unnamed mineral

Uranyl carbonate phases have been identi edon radioactive materials that resulted from the

nuclear accident in the Chernobyl No 4 reactor Alteration products collected from the Chernobyllsquolavarsquo were identi ed by XRD and energyd i s p e r s i v e s p e c t r o s c o p y ( E D S ) a sNa4(UO2)(CO3)3 along with Na3H(CO3)2 2H2OUO3 2H2O Na2CO3 H2O UO4 4H2O and

Na3

Na3Na3

a

asin120

c

(a) (b) (c)

(d)a

Na1

Na2

Na3

asin120

c

(e)

FIG 1 The structure of Na4(UO2)(CO3)3 (a) Uranyl tricarbonate cluster (b) Na33O11 trimer (c) heteropolyhedralsheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na33O11 trimers projected onto(001) (d) the structure projected onto (010) Na1 Na2 and C are omitted (e) the structure projected onto (010) (f)the structure projected onto (001) with Na(3) polyhedra omitted (g) the structure projected onto (001) The CO3

groups are shown as black triangles the UrO6 polyhedra are light grey and the NaOn polyhedra are dark grey

2AO

2B

a

a

2AO

2B

a

a

(f) (g)

302

YAPING LI ETAL

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

UO2(CO3) (Burakov et al 1999) The phase wehave studied may be the same as one of the Nauranyl carbonates forming at Chernobyl

Acknowledgements

This research was supported by the United StatesDepa rtm en t o f Ene rgy Env ironmen t a lManagement Sciences Program (DE-FG07-97ER14820)

References

Brese NE and OrsquoKeeffe MO (1991) Bond-valenceparameters for solids Acta Crystallogr B47192 7

Burakov BE Strykanova EE and Anderson EB(1999) Secondary uranium minerals on the surface ofChernobyl lsquolavarsquo Mat Res Soc Symp Proc 4651309 11

Burns PC (1999) Crystal chemistry of uranium Pp23 90 in Uranium Mineralogy Geochemistry andthe Environment (PC Burns and RJ Finch editors)Reviews in Mineralogy 38 Mineralogical society ofAmerica Washington DC

Burns PC Ewing RC and Hawthorne FC (1997)The crystal chemistry of hexavalent uraniumpolyhedron geometries bond-valence parametersand polymerization of polyhedra Canad Mineral 35 1551 70

Burns PC Miller ML and Ewing RC (1996) U6+

minerals and inorganic phases a comparison andhierarchy of crystal structures Canad Mineral 34845 80

Clark DL Hobart DE and Neu MP (1995) Actinidecarbonate complexes and their importance inactinide environmental chemistry Chem Rev 9525 48

Douglass M (1956) Tetrasodium uranyl tricarbonateNa4UO2(CO3)3 Anal Chem 28 1635

Finch RJ Cooper MA Hawthorne FC and EwingRC (1999) Re nement of the crystal structure ofrutherfordine Canad Mineral 37 929 38

Ginderow D and Cesbron F (1985) Structure de laroubaultite Cu2(UO2)3(CO3)2O2(OH)24(H2O) ActaCrystallogr C41 654 7

Grice JD and Ferraris G (2000) New mineralsapproved in 1999 by the commission on newminera ls and mineral names Interna tionalMineralogical Association Canad Mineral 38245 50

Li Y Burns PC and Gault RA (2000) A new rare-earth-element uranyl carbonate sheet in the structureof bijvoetite-(Y) Canad Mineral 38 153 62

Mandarino JA (1999) Fleischerrsquos Glossary of MineralSpecies 1999 The Mineralogical Record Inc Tucson AZ USA

Mayer H and Mereiter K (1986) Synthetic bayleyiteMg2[(UO2)(CO3)3] 18(H2O) thermochemistry crys-tallography and crystal structure Tsch Miner PetrMitt 35 133 46

Mereiter K (1982) The crystal structure of liebigiteCa2UO2(CO3)3 ~ 11H2O Tsch Miner Petr Mitt 30 277 88

Mereiter K (1986a) Crystal structure and crystal-lographic properties of a schrockingerite fromJoachimsthal Tsch Miner Petr Mitt 35 1 18

Mere i t e r K (1986b ) Syn the t i c swar t z i t e CaMg[(UO2)(CO3)3] 12H2O and its strontium

asinb

bsin a

csin a

asin g

(a) (b)Ca

UC

S

C

FIG 2 The structure of schrockingerite (a) Structure projected along [001] grey circles represent Na cations (b)structure projected along [010] black circles represent H2O groups

CRYSTAL STRUCTURE OF NA4(UO2)(CO3)3

303

analogue SrMg[(UO2)(CO3)3] 12H2O crystallogra-phy and crystal structures Neues Jahrb MineralMh 481 92

Mereiter K (1986c) Neue Kristallographische Datenueber das uranmineral andersonit Anz OesterrAkad Wiss Math-Naturwiss K13 39 41

Ondrus P Veselovsky F Skala R Cisarova I

Hlousek J Fryda J Vavrin I Cejka J andGabasova A (1997) New naturally occurring phasesof secondary origin from Jachymov (Joachimsthal)J Czech Geol Soc 42 77 108

[Manuscript received 19 July 2000revised 8 January 2001 ]

304

YAPING LI ETAL