CRYSTAL STRUCTURESIN THE UNIVERSITY OF BARCELONA.

APPLIED SOLUTIONS

X. SOLANS AND M. FONT-ALTABA

Department of Crystallography, Mineralogy and Mineral Deposits

University of Barcelona

In the area of Barcelona there exists at present four important Centerswhere different types of X-ray diffraction are carried out. These laborato-ries belong to the three Universities of the Catalan Government and to theHigher Scientific Research Council (Consejo Superior de InvestigacionesCientificas) of the Central Government. They are:

A) University of Barcelona:a) Department of Crystallography, Mineralogy and Mineral Deposits;

b) Scientific Technical Services.

B) Polytechnic University of Catalonia:

a) Department of Chemical Engineering, Group of Macromolecular

Structures.

C) Scientific Research Council of Spain (Consejo Superior de Investigacio-nes Cientificas):

a) Institute of Material Sciences, Crystal Structure Research Group;

b) Institute of Earth Sciences (Institute Jaime Almera), Powder X-ray

Diffraction Group.

D) Autonomous University of Barcelona:

a) Department of Geology, Crystal Structure Determination.

In the University of Barcelona X-ray diffraction is in existence in two

Departments, the Department of Crystallography, Mineralogy and Mine-

ral Deposits and the Scientific Technical Services. The first is a complex

center in the Faculty of Geology created in 1912 as a group to study mine-

]Butll. Soc. Cat . Cicn.], Vol. Xll, Num. 2, 1991

200 N. SOLA NS - A/. R) '% -,11, L,IIA

rals and general mineralogy; crystallography was necessary to understandmineralogical properties and, in the course of time and as a result of perso-nal efforts, it has become one of the most important parts of the group.Goniometry started in the twenties with the study of the geometricalforms of crystals and, thereafter, their symmetry. In the thirties X-ray dif-fraction-in single crystals was developed with some special studies publis-hed in Zeitschrift fur Kristallographie. Our Civil War stopped this resear-ch for several years and the isolation of our country during the World Warand the forties and fifties prevented us from having high-level contactswith world crystallographic science. We wish to recall the difficult timesovercome by the effort of Professors P. Pardilla and J. L. Amoros, whoworked in Barcelona on crystallography and who were known in theworld of our science. Today, the Department is a center with a high levelof scientific work.

The second center was created about twenty years ago as a group

working in the field of spectrographic analysis; after some time, it was as-

sociated with an electron microscope group and was transformed into a

scientific technical service of the University. At present it has electron mi-

croscope equipment (8 transmission and 3 scanning microscopes with mi-

croanalysis accessories), complete modern spectrographic equipment

(normal, ultr.:iolet and infrared), some other special techniques and for

the last four ye.. rs a powder X-ray diffraction group (two Siemens and one

Enraft-Intel diffractometers).

The Department of Crystallography, Mineralogy and Mineral Depo-

sits is divided to four research units, as can be seen from figure 1.

A. Raw Ceramic Materials. Archaeometry, ceramics and applied mi-neralogy. UNESCO n.° 331203, 250611, 550599 and 550502.

Research work on the synthesis and process of materials for ceramicuse; characterization and application; utilisation of minerals for industryand construction.

B. Mineral Deposits. Study and research of the mineral deposits in

Catalonia. UNESCO n.° 250610 and 250611.

As-Au mineralization in the Pyrenees (Ordovician) and concentra-tion inside fissures by hydrothermal solution; As-Au and W in hvdrother-mal concentrations near granite intrusions and metasolnatism aureola(skarn) in the Central and Eastern Pyrenees; Pb-Zn-Cu and Mn sulfurs inseries of the Lower Carboniferous; ha-E-Pb-Zn-Ag mineralization asso-ciated with pre-Triassic paleosurfaces.

[ButIl. Soc. Cat. Cien.], Vol. XII, Num. 2, 1991

(,'R) ST.II SIY ( (.71RIS 201

ROW CERAMIC MATERIALS

SynthesisProcessCharacterizationAppication

MINERAL DEPOSIT

Deposit searohCharaolerizatlonMineralogeneals

DEP. CRISTAL.LOGRAFIA, MINERALOGIAI DIPOSITS MINERALS

UNIVERSITY OF BARCELONA

MOLECULAR ALLOYS

TheoryExperimental Phase DiagramsThermoarWysleApplications: Energy storage

STRWTLRAL CRYSTALLOGRAPHY

Synthesis of doubled oxideStructure detrrntlatbnPhew Transitions

Fig. 1. The schema of the research units in the Department of Crystallography, Mineralogy

and Mineral Deposits.

C. Molecular alloys and isomorphism. Theory of isomorphism; expe-rimental determination of phase diagrams; forecast, elaboration and cha-racterization of new materials to be used as energy concentrate agents.

UNESCO n.° 221104, 221101, 221021, and 332205.Purifying, crystallographic characterization and the thermodynamics

of compounds; creating new molecular alloys by different methods; expe-

rimental equilibrium diagrams between phases, theoretical diagrams and

relations between them; sincrystallization criterion determination bet-

ween organic compounds; prototype construction to simulate energy in a

real situation; thermal cycles (melting-crystallization) of different weights

to obtain the energetic yield of special organic products.

[Butll. Soc. Cat. Cicn.], Vol. X11, Num. 2, 1991

202 A. ML;I.AS - V. FOMI 1/ IA/Li

The group collaborates with the Laboratoire de Cristallographic of

Bordeaux University and the Thermodynamics Laboratory of Utrecht

University; and also with the Department of General Physics of Barcelona

University.

U. Structural crystallography. Crystal and molecular structure analy-sis; crystal symmetry; growing crystals in solid state (hexaferrites); phasetransitions. UNESCO n." 221101, 221104, 230326, 230618 and 241599.

Resolution of crystal structures from single crystal X-ray diffractionspectrum; synthesis, crystal growth and structural studies of hexaferrites;scientific support for the X-ray diffraction group of the Scientific and Technical Services of the University; crystal symmetry studies with the go-niometer; optics of crystalline compounds and identification of materialsby optical methods; n (real) and k determination of light absorbing crys-tals; microanalysis and identification of layers of paint of wall paintings of11th to 14th century date and oil and wood ones of 15th to 16th centurydate.

The main scientific techniques used by the Department are shownschematically in figure 2. X-ray diffraction is the most important methodto carry out the wide range of research work with the connection to thegeneral computer of the University and the use of several PC's and micro-computers with crystallographic software of a greater or lesser degree ofcomplexity. Goniometry, optical and electron microscopy, and thermalaccessories are basic as complementary methods. A substantial number ofdifferent techniques are used in ceramics, thermoanalysis and crystalgrowth. Mineralogical studies and mineral deposits search have specialfield methods and laboratory techniques.

X-RAY DIFFRACTION ♦ THERMOANALYSISDSC: N2 - 1000CTG: 25-1000C

CERAMIC MATERIALS I MicrocalorimetreCHARACTERIZATION

OPTICAL MICROSN2 - 300CPHOTOGRAPHY

ELECTRON MICROSCOPE I VIDEOSEM, TEM

COMPUTATIONAL MICROPROBE SYNTHESISTECHNIQUES

F1,_ 2. The schema of main scientific techniques used by the Department.

]Butll. Soc. Cat . Cien.], Vol. XII, Num. 2, 1991

CKYSTAL STRUCTURES 203

The Department has two single crystal diffractometers:

a) a PHILIPS 1300 (eleven years old) with low temperature and grap-

hite monochromator; the equipment is ruled by a microcomputer with the

corresponding programs to work in a completely automatic form. It was

modified to collect data on a PC computer, instead of on the original rib-

bon system. The programs in the PC computer give us the possibility to

correct data for Lorentz-polarization, to reduce the values to an E, and

enable us to perform some corrections of absorption.

b) a new ENRAFT-NONIUS CAD4 apparatus, ruled by a micro-

computer, with a complete system of software in order to work complete-

ly automatically, connected to a series of two PC computers for contro-

ling the experimental data. Data from the detector and amplifier are collec-

ted on one PC, and they are corrected for Lorents-polarization, any appa-

ratus error detected, and absorption of the parameters of the cyrstal form

and symmetry are given. On the other, all corrected data are reduced to an

E, and a set of special software permits the calculation of the structure of

the sample in some cases (very good crystals, with a small number of

atoms), or facilitates work with the corrected experimental data in other

fields.

In addition, the Department has other X-ray generators equipped

with Weissenberg and Precession cameras, and other special cameras for

different types of experiment (Laue research work, twinned crystals, etc.).

Figure 3 is the scheme for X-ray diffraction (including the powder diffrac-

tion described below).

The research work on crystal and molecular structures which arc sol-

ved by the apparatus and methods explained, makes use of complementary

techniques to establish the morphology and external appearance of the

crystals together with their optical properties.Goniometry was the first method used in the Department to study

the morphology of well crystallised minerals, and to stablish habitus of

these coming from different origins. A two limbus goniometer of good

construction, brought from Germany in 1926, gives angles between faces

with ± 1' and, in special cases, ± 30". Calcite, quite abundant in Catalo-

nia, with around 120 habitus described by the Goldschmidt Atlas; Gar-

nets, with different habitus at different local points, differences in morp-

hology connected with their genesis (Sunagawa research works); variation

in the position of the surface areas on the same face of a crystal, as in the

case of Galena, Quartz, Diamonds, etc.; these were the lines of research

followed in the twenties and thirties, together with the study of the morp-

hology of cyrstals going to be examined by X-ray diffraction, which was

of assistance because of the need to position the crystal in an exact situa-

tion in old X-ray cameras. Today, the goniometcr is used to study the ex-

[BLtII. Soc. Cat . Cicn.], Vol. X[[, Num. 2, 1991

204 _A. SU1.1M tI. FO.AT- 1LI9B.1

PHILIPS 1300SINGLE CRYSTALDIFFRACTOMETERROOM T

PHILIPS 1100CAMERAS

WEISSEMBE RQ

PRECESSION

ENRAF CAD4SINGLE CRYSTALDIFFRACTOMETER

ROOM AND LOW T

ENRAF F590 - INESPECIAL POWDER

SIEMENS D500SPECIAL POWDER

STATIC LOW AND HIGH T

FILM DIFFRACTION

SIEMENS D500TANDARD POWDE

ARCH DETECTOR (120)

KINETIC

LOW AND HIGH T

STANDARD QUALITATIVE

AND QUANTITATIVE ANALYSIS

Fig. 3. The schema to X-ray diffraction equipment at the Univ crsity of Barcelona.

ternal symmetry of series of crystals to deduce variation in habitus as op-posed to temperature in some industrial crystals (pictorial materials).

Optical crystallography was another technique used to find out theoptical properties of new crystals, like optical ellipsoid, optical indexes (u,

R, y), position of the axes of the ellipsoid related to crystallographic svm-metry, and general optical conditions such as color, transparency, etc.(Fig.4 and 5). The Department has a number of polarizing microscopes forstudent use, and substantial range of optical equipment of photosensitivesystems for light between 250 nm to 1100 nm, with a system of quartz ob-jectives and diaphragms that do not stop ultraviolet or infrared light. Thisequipment is connected to a microelectronic system to produce an auto-matic management of the scanning stage and provides the facility to calcu-late the optical density of light statistically, in transmission and reflection.Some research papers on properties of adsorbing crystals, and the clacula-tion of n and k, have been published (fig. 6).

The structural crystallographic research unit is formed at present bytwo specific groups:

jButI1. Sur. (:at. Cc11.1, Vol . ?ill, Num. 2, 1991

UR KSTAL STRUCTURES 205

Fig. 4. Cobalt ethvlenediaminetetraacetate (CoELTA) crystal. (Prom PhD of M. Pont-Bar-dia at the University of Barcelona).

intcilrrrnfc IILI ic rein tv^^, E,ue,ii ,t

I Butll. Soc. Cat. Cicn.], Vol. XII, Num. 2, 1991

206 .A. SQL. 1.\.S - .U. FO.A,I Al 1,11)"A

30%

28 %

26 %

24 %

vibration parallel to [001]

.- vibration parallel to [010]

vibration parallel to [100]

600 . rim

reflectance values in oil of

ENARGITE 54 As Cu3

standard. SIKA from CC M

14 %

^12% -

REFLECTANCE VALUES IN A/R OF ENARGITE, S4 As Cu3

standard . SIKA from C.0 M

500

vibration parallel to [001]

vibration parallel to 10101

107.vibration parallel to (100)

450 500 550 600 650 .1,nm

3.4

32

30

28

Ik

06

04

REFRACTIVE INDICES AND ABSORPTION COEFFICIENTS OF ENARGITE

vibration parallel to 001]

vibration parallel to (001]

'vibration parallel to [010

vibration parallel to (00]

vibration parallel to [010

vibration parallel to 1100]

- 500' 600 . rvn

Fig. 6. Keflectance values in air, Ra, and oil, Ko, with the calculated n (refractive indexes) and

k (absorption coefficients) of enargite, S1A,Cui. (Front M. A'cndrell, A. Lopez-Soler and J.

M. Bosch-1:igueroa).

[Budl. Soc. Cat. Cicn.J, Vol. XII, Ntim_ 2, 1991

CR) tiT. l/ STRC (T( R15 7

a) One, directed by professor Salvador Gali, carries out research ongrowing crystals in the solid state (essentially hexaferrites), and the struc-tural analysis of some of them. In the majority of cases, the crystals are sosmall that it is necessary to use the powder diffraction method to obtainX-ray information. The crystal structure of the samples is known, so theRietweld method is used to obtain more accurate information on the dis-tribution of specific atoms by blocks. This group has a series of furnaceswith temperatures up to 1600", in normal or controlled atmospheres, withspecial electronic and mechanical systems that can be applied to the furna-ce to grow crystals in specific conditions. They have published about 30research papers, in Afinidad, Anales de Quimica, Journal of AppliedCrystallography, Material Research Bulletin, N. Jb Miner. Mh., etc.

b) The other, directed by professor Xavier Solans, carried out resear-

ch work on crystal and molecular strucure analysis of samples coming

form different laboratories of the University of Barcelona or from other

Spanish Universities such as Oviedo, Bilbao, Zaragoza, Valencia, Murcia,

Badajoz, Granada, etc. The research of this group has different connec-

tions with foreigh Departments such as the Institute of Crystallography of

Moscow and the Department of Fine Organic Synthesis of Sverdlovsk

(Urals Division) of the USSR Academy of Sciences, through the Institut

d'Estudis Catalans; the Laboratoire electrochimique des Metaus de Tran-

sition of the Orsay University (Paris); the Laboratoire de la Chimie de

Coordination of the Paul Sabatier University (Toulouse); the Department

of Inorganic Chemistry of the Autonomous National University (Mexico)

and the Guanajuato National University of Mexico; and the Chemistry

Department of the National University of Bogota. Fig. 7 and 8 show the

schema of the general hardware and software used for the solution and re-

finement of the structure of crystals. As an example of the work of this

group the drawing solutions (ortep and moldraw) of the 6,7-dimethyl-2,3-

bys (2-pyridyl) quinosaline-hexafluoroacetylacetonatecobalt (11) (Co

(DMeDPQ) (hfacac)2) arc shown in figures 9 and 10.

We wish to emphasize the main problems in crystal structure deter-mination: the quality of crystals and the purpose of determination. Theworking methods differ according to the purpose of crystal structure de-termination, high accuracy implies a higher number of reflections obser-ved, or a higher time in the diffractometer to the detriment of the numberof crystal structures determined in a year. Poor crystal quality produces alower number of reflections observed which influences in solution obtai-ned. A short study of the influence of the number of reflections observedin the different stages of analysis, which are shown in fig. 11 to 14, is ex-plained in the next section.

IButll. Soc. Cat . Cicn.I, Vol. XII, Num. 2, 1991

208 A. SO!.t.A'S-.11. /O:v7-.1L/'IB 1

DIFFRACTOMETER

IBM PS2/55

IBM 3080/2

PLOT TER

GRAPHICAL DISPLAY

PA/NT JET

LASER PRINTER

Fig. 7. The schema of the hardware crystal structure determination.

CRYSTAL STRUCTURE DETERMINATION

DIRECT METHODS PATTERSON

MULTAN84 SHEL X76

SHELX86 SHELX86

FROM PARTIAL STRUCTURE

D/RD/F

REFINEMENT

SHELX76

GRAPHICALMOLDRAW

ORTEP

PLUTO

FROM POWDER DIFFRACTIONRIFT VEL D

Fig. 8. The schema of the software crystal structure.

jBudl. Soc. Cat. Cien.], Vol. XII, Num. 2, 1991

CRYST.11. STRUCTURES 209

Fig. 9. Drawing solution of the 6,7-dimethyl-2, 3-bys (2-pyridyl) quinosaline hexafluoroace-

tvlacetonate cobalt (II) (C0cH,_N4O4P6Co) molecule with ORTEP program. (Prom A. Es-

cuer, R. Vicente, T. Comas, J. Ribas, M. Gomez, X. Solans, D. Gattesh and C. Zanchini;

Inorganic Chimica Acta 131 (1991) 51-60).

A) Multan 84. The number of reflections used in the Multan programis independent of the number of reflections introduced, because it is defi-ned by the number of non-hydrogen atoms in the unit-cell, the spacegroup and the value of normalized structure factor, but all the reflectionsintroduced are used determine the Wilson plot, poorer result being produ-ced as fewer reflections are introduced. This alters the normalization ofstrrcture factors, convergence mapping and the best phase set, and as a re-sult the solution.

B) Shelx 86 (direct methods). The number of reflections used in refi-nement and the number of non-negative quartets are bounded by the pro-gram, as the fewer the reflections introduced in the program, as the higher

[Butll. Soc. Cat. Cicn.], Vol. XII, Num. 2, 1991

,I- .A. SO! l\S-_ t/. IO\/ 1// 11i_1

I ig. IC. Ur.twing Solution of the 6,7-dimcili l 2, 3 bt 5 (? 1) .% 1 quinosaline hcya!luoio.i-

cetvlacetonate cobalt (11) (C,H,,N4U4F,,Co) unit cell structure by means of ML)LI)RAW

program. (From A. Fscuer, R. Vicente, T. Comas, J. Ribas, M. Gomez, X. Solans, D. Gattes-

hi and C. 'Lanchini; Inorganic Chimica Acta 181 (1991) 51-60).

the number of non-negative quartets obtained , and the structure is not de-

termined.

C) Patterson. No incluence of the number of reflections introducedcan be observed.

I)) Refinement. The influence in refinement is doubled, it alters the

speed of refinement and the accuracy. The velocity can be observed fromthe equation defining the computed structure factor, a higher slope beingobserved for contributions of heavy atoms or reflections of a high order,

so, differences between F; and F show less dispersion of refined parame-ters if they correspond to heavy atoms or if reflections of a higher order

are used. As the values of first and second derivatives depend on the oldparameters, the refinement shows minimum wavering when reflectionswith higher Miller indexes are used. The influence of the accuracy of re-sults is shown in the adjoining schema, and as a higher number of reflec-

[Butll. Soc. Cat. Cicn.j, Vol. XII, Num. 2, 1991

CRYSTAL .STRIJCTURL.S

OOORDENADMS ATOMCAS

XI

-- C,h.1 ^C, 11•4 "'tt F.,11.1 -F4,11.4

FACTOR DE ESCALA

C

K

AOITACION TERMCA

Nar-I4

3

6

UI

- C,11•4 -C,11.1 ^ Ft,11.1 - F., 6.4

FACTOR DE OCUFACION

2

10 1 2 Z 4 6 6 m1T- W N 12 13 K 16 16 17 16 11 20

91

-- 1 ..1 a - C - F.

Fig. 11. Influence of the number of observed reflections in refinement the speedFc=KAj

Al = fl gj exp(2ihxj) exp(-hUjh)

tions is used, we obtain fewer standard deviations, less dispersion in equi-valent bond lenght and angles, although the R index increase (in spite ofthe fact the R-index tends to diminish when better is the structure)..

E) The quality of crystal. A random error has been introduced intothe values of structure factors observed, increasing a percentage of theirvalue randomly plus or minus. The results are obvious: increasing theerror, means an increase in the R value and dispersion between equivalentbond lengths.

Our group is carving out the determination of the atomic structure ofmagnetic crystals, previously studied as regards their magnetic propertiesin the Faculty of Physics, in order to obtain information on the effects ofdirections of strong bonding, and also, through powder diffraction at dif-ferent temperatures, the possibl changes appearing. In addition, we arenow studying differences in structure transition produced by low tempe-rature effects to obtain the best data for bonds and angles of special struc-ture crystals.

211

JButll. Soc. Cat . Cien.], Vol. X11, Num. 2, 1991

113 \. MI l\1 ll . /()\I 1/ / 1/ 111

DETERMINACION DE B POR WILSON PL

N retlexiones introducldas

30

R KARLE PARA LA SOLUCION CONMEJOR CFOM

R Karle

23

20

15

10

0--1000 3600 5000

N. reflexionea Introducidas

Fig. 12. Influence of the number of observed rctlections in 1IUII AN)4.

[Bull. SOC. Cat . Ciin.], Aul. AII, Num. 2, 1991

N. REFL . UTILIZADOS EN SHELX86

1000

BOO

eoo

400

400

N. ref. util.

760

0 t ^^^y7760 4000 ]60^ ffe0 X000

N. TPR . UTILIZADOS EN SHELX86

76

s0

16

10

6

N. TPR. utll. (Thousands)

N. Ref . Intro d.

a .u. - .1i..6..

N. OUARTETOS EN SHELX86

N. O uartetoe

e

6

N. Ref. Introd.

O.1

7

... n.lo• oao - e..rl•lo. .ui

N. ReI. intro d.

TB11 •n A •II• TB11 •. .t. E

FIGURAS DE MERITO EN SHELX86

o.s

0.16

0.06

0 ^-'760

CF OY

I^i^. 13. Influence of the number of obsewrved rrflectiuns in SHELX86.

ree f:eo ^ooe

1^1

!' I^

7760 1000

N. Ref . Introtl.

[Buhl. Soc. Cat. Cic n.], Vol. XI1, :V um . 2, 19Y1

''-14 X. MLA V'S - M. !0,Vi'-A!.T 1 BA

Dispers ion (1E-4)100,

so

so

40

20

0%

Error introducido

Dispers ion

1.9 • V/1000R0.26 r---

0,2

0.15

0,1

6o

60

40

30

20

0.0610

20%

0--^_ 0L ^ i _.. L _.--1_.-0% 20% 0% 20%

Error introducido Error introducido

- R - DMtancia media

Fig. 14. Influence of measurement errors in the refinement.

The group have published nearly 250 papers in journals such as ActaCrystallographica, Inorganic Chimica Acta, Inorganic Chemistry, Inter-national Journal of Peptids and Protein Research, Journal of AppliedCrystallography, Journal of Biomolecular Structure and Dynamics, Jour-nal of Chemical Research, Journal of Chemical Society (Chemical Co1n-munications and Dalton Transactions), Journal of Crystallographic andSpectrocopic Research, Journal of Organometallic Chemistry, Organo-

jRutll. Soc. Cat . Cien.], Vol. XII, Num. 2, 1991

CRYSTAL STRUCTURES 215

metallics, Polyhedron, Powder Diffraction, Tetrahedron, Transition Me-

tal Chemistry, Zeitschrift fur Kristallographie, Afinidad, Acta Geologica

Hispanica, etc.

In normal circumstances, taking in account the availability of new

equipment and the damage to old pieces, and also the quality of crystals

received for their structure to be solved, only about 50% of crystals ha-

ving a sufficiently high quality for X-ray diffraction, the structural crysta-

llographic group arc able to evaluate between 60 and 80 structures per

year, at present.

The Scientific Technical Services of the University of Barcelona has a

Powder X-ray Diffraction group for the general services of the University

and for services to Industry. The equipment of the group consist of three

diffractomcters on powder samples, two Siemens D500 and one Enraft

with an inel detector. One of the Siemens works with standard samples gi-

EXTERNAL OUTPUT

PHILIPSFONCTIONAMENT

I

IBM PS2/30

tMICROVAX 2000

CAD

IBM PS2/30

DACO P

IBM PS2/60FONCTIONAMENT

E$ ALUATION

SEARCH JCPDS

PROFILE ANALYSIS

QUANTITATIVE ANALYSIS

INDEXATION

TREOR

AFFMAIL

IBM PS2/60

EXTERNAL OUTPUT

Fig. 15. The schema of the software used to solve the powder diffraction data.

]Butll. Soc. Cat . Cien.], Vol. XII, Num. 2, 1991

216 A. SQL. 1.AS - .1 1. LY)\7-.1L71111

ig. 16. f cc troll micrusa)pc photograph Of tact, I- I )I\ dcric.itc crc,tak.

(Butll. Soc. Cat. Cicn.I, Vol. X11, Num. 2, 1991

C R ) ^/ Il 1/R( ( 7l hl ^ 'I-

ving results to users to identify materials and to provide the standard spec-

trum of new compounds; the other Siemens has low and high temperature

accessories and is normally used by the molecular alloys and isomorphism

group of the Department; both Siemens diffractometers are arranged to

work in equilibrium in order to attend all possible users. The Enraft-Intel

diffractometer has an arch detector of 120" and its service is essentially

for kinetic processes; the speed in obtaining the spectrum is fast, between

3 and 15 minutes, and the accuracy of the position and intensity of peaks

is good. Every piece of equipment is ruled by a microcomputer, which is

connected to a personal computer in order to be able to obtain and work

with data (the schema is shown in fig. 15). All software on powder diffrac-

tion (Siemens special software) is operated with one PS2/30 and two PS2/

60 IBM computers.

Electron microscopy, both of the transmission and scanning type, is

a form of a technical assistance used to study the form of microcrystals,

the microanalysis and the map distribution of elements in very small crys-

tals. In fig. 16 two crystals of ethylenediaminetetraacetate derivates are re-

presented, and in fig. 17 a mapping of the elements in a sample of pictorial

I i;. 17. yI.tppinp; of the clcmcnt. III a sample of pictori.11 material with their Supcrintpotition

xt as to provide a combination of thorn.

JButll. Soc. Cat. Cicn.l, Vol. XII, Nin. 2, 1991

215 X. SOL.-la'S -M. 1O v T:1 LT 1 BA

material with their superimposition so as to provide a combination ofthem. The colors of the mapping are not real colors, the photograph has256 different types of white, grey and black, but every one of there greysis associated with one series of imaginary colors given to the drawings thatcan be seen.

The electron scanning microscope with microanalysis by EDX is ab-solutely necessary to study the pictorial materials of wall paintings of11th, 12th and 13th centuries, thoses on wood of 15th century, and in ge-neral to do any research work of this type on oil paintings.

ABSTRACT

In the area of Barcelona there exists at present four important Centers where dif-ferent types of X-ray diffraction are carried out. In the University of Barcelona X-raydiffraction is in existence in two Departments: the Crystallography, Mineralogy andMineral Deposits, and the Scientific Technical Services.

The first is a complex center in the Faculty of Geology created in 1912 as a groupto study minerals and general mineralogy; crystallography was necessary to unders-tand mineralogical properties and, in the course of time and as a result of personal ef-forts, it has become one of the most important parts of the group. Goniometrv startedin the twenties with the study of the geometrical forms of crystals and, thereafter,their symmetry. In the thirties X-ray diffraction in single crystals was developed withsome special studies published in Zeitschift fur Kristallographie. Our Civil War stop-ped this research for several years and the isolation of our country during the WorldWar and the forties and fifties prevented us from having high-level contacts withworld crystallographic science. We wish to recall the difficult tiems overcome by theeffort of Professors F. Pardillo and J. L. Amoros, who worked in Barcelona on crys-tallography and who were know in the world of our science. Today, the Departmentis a center with a high level of scientific work.

The second center was created about twenty years ago as a group working in thefield of spectrographic analysis; after some time, it was associated with an electronmicroscope group and was transformed into a scientific technical service of the Uni-versity. At present, it has electron microscope equipment (8 transmission and 3 scan-ning microscopes with microanalysis accessories), complete modern spectrographicequipment (normal, ultraviolet and infrared), some other special techniques and forthe last four years a powder X-ray diffraction group (two Siemens and one Enraft-In-tel diffractometers).

A detailed description of X-ray diffraction in both Departments are explained,with some possible solutions to the problems arising from the developing of the ana-lysis of crystal structures.

[Butll. Soc. Cat . Cicn.[, Vol. XII, Num.2, 1991

(.R)ST.II S%RL(.7( RLS '19

REFERENCES

The crystallographic research papers of the Department of Crystallogra-phy, Mineralogy and Mineral Diposits have been published in the standardjournals of this field mentioned in the present text.

[Buell. Soc. Cat. Cicn.], Vol. XII, Num. 2, 1991