I N l ti t I t fIce Nucleation at Interfaces

Angelos MichaelidesAngelos Michaelides

London Centre for Nanotechnology & Department of Chemistry, University College Londony g

&

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany

Main co-workers: Javier Carrasco (FHI), Xiaoliang Hu (UCL), Bo Li (FHI), Limin Liu (UCL), Karina Morgenstern, Ding Pan, Biswajit Santra (FHI),

Matthias Scheffler (FHI), and Enge Wang

IInterfaces:CCatalytic & EEnvironmental

www.chem.ucl.ac.uk/ice

H O solid interactions play a central role in electrochemistryH2O-solid interactions play a central role in electrochemistry, atmospheric science, corrosion, catalysis, fuel cells, H2 production,

“nanomachines” …an endless list

http://mems.sandia.govhttp://mems.sandia.gov

The earth is getting hotter & more polluted, cleaner forms of energy are desired, and devices are getting smaller.

Our work: chemistry and physics of water-solid interfaces…aiming at an atom-by-atom structural, dynamic, and electronic understanding

1

Ice Nucleation is Important!

• Water freezing is a key physical process on earth …but pure

Ice Nucleation is Important!

water is not easy to freeze!....homogeneous freezing point is -40 ºC

• Typically an ice nucleation agent is required

Ice nucleation Threshold1:

Typically an ice nucleation agent is required.

• ‘Natural’ clays: -5 to -12 °C

AgI 3 to 6 °Cprecipitation

• AgI = -3 to -6 °C

• Metals, Metal oxides = -5 to -12 °C

•• Cholesterol =Cholesterol = --1 to1 to --22 °°CCCholesterol Cholesterol 1 to 1 to 2 2 CC

1Pruppacher & Klett, Microphysics of Clouds and Precipitation

What Makes a Good Ice Nucleating Agent?

• Chemical nature of Substrate (Reactivity)

• Structure of substrate

What Makes a Good Ice Nucleating Agent?

Structure of substrate

• Defect concentration and nature

• Particle size…

AgI as seed for ice nucleation in clouds

An old truth or an old myth?

I II I 4 50 Å4 50 Å

General: B. Vonnegut, J. Appl. Phys. 1947, 18, 593; Pruppacher & Klett, Microphysics of

Ice IIce Ihh ~4.50 Å~4.50 Å

Clouds and Precipitation Metals: Thiel & Madey, Surf. Sci. Rep. 1987, 7, 211.

2

Surface science, e.g. STM:Transition metals

4 43 Å

Surface science, e.g. STM:Transition metalsexcellent model systems…

Ni Cu4.43 Å

-1.6 %9H9H22O/AgO/Ag6H6H22O/CuO/Cu

Pd Ag5.00 Å

+11.1 %

4.77 Å

+6.0 %

• Density Functional Theory (DFT)for electronic structures (Born Oppenheimer approximation)

Pt Au

Oppenheimer approximation)

• Basis set of planewaves

• Periodic Slab Models

• Core electron-ion interactions treated with pseudopotentials

Ice IIce Ihh ~4.50 Å~4.50 Å

pseudopote t a s

• Electron exchange and correlation with GGA (PBE)

CASTEP d• CASTEP code

Ch i t d h i f t lidMonomers (Pd)

Chemistry and physics of water-solid interfaces…aiming at an atom-by-atom structural and dynamic understanding

Monomers (Pd)

structural and dynamic understanding

Many simple questions to address:Cl t (C ) Many simple questions to address:

How do water monomers bind to solid surfaces

(atomic and electronic structure)?

Clusters (Cu)

( )

What about water clusters…will they form, what will

their structures (atomic and electronic) be?Overlayers (Pd)

How do water clusters diffuse, grow, and nucleate?

What role does the structure and reactivity of the

Overlayers (Pd)

y

substrate play, especially hydroxyl groups?

STM Images and Movies: Miquel Salmeron (Berkeley) & Karina Morgenstern (Hannover)

3

Water monomers on Flat Metal Surfaces

• Water has a large dipole moment (2.6 D),

Water monomers on Flat Metal Surfaces

g p ( ),

assumed to yield an upright (vertically

oriented molecule upon adsorption)

•…is this correct & what about the

adsorption site?

Upright (vertical) Flat (parallel)Upright (vertical) Flat (parallel)

Water monomers on Flat Metal SurfacesWater monomers on Flat Metal Surfaces

Pd{111} Pt{111} Ru{0001} Rh{111}Pd{111}, Pt{111}, Ru{0001}, Rh{111},

Ni{111}, Cu{111}, Ag{111}, Au{111}, Al{111}

and Al{100}

Michaelides et al., Phys. Rev. Lett., 90, 216102 (2003)

Michaelides, Alavi, and King, J. Am. Chem. Soc. 125,

2746 (2003)( )

Michaelides et al., Phys. Rev. B. 69, 075409 (2004)

4

Water monomers on Flat Metal SurfacesWater monomers on Flat Metal Surfaces

Electron density rearrangement Water orbitals (gas phase)

Green = -Blue = +O

Electron density rearrangement Water orbitals (gas phase)

Ru��(H(H22O/Ru)O/Ru) –– ��(Ru)(Ru) –– ��(H(H22O)O)-20 -15 0-10 -5

E - EHOMO (eV)

The bonding between water and metals can be understood through a k l t i t ti di t d b 1b d 2 h b idi tiweak covalent interaction mediated by 1b1-dz2 hybridization

Water dimers on Flat Metal Surfaces

Eads (eV/H2O) O-O (Å) O-M (Å)

Water dimers on Flat Metal Surfaces

Cu 0.35(monomer: 0.22)

2.70(Cu-Cu: 2.58)

2.14 (monomer: 2.30)

Pd 0 43 2 67 2 22Pd 0.43(monomer: 0.31)

2.67(Pd-Pd: 2.78)

2.22 (monomer: 2.32)

Ag 0.27 2.75 2.46 (monomer: 0.15) (Ag-Ag: 2.93) (monomer: 2.62)

• H bond acceptor makes a “weak” water-metal

bond

H b d d f “ t ” t t l b d• H bond donor forms a “strong” water-metal bond

• H bond (appears to be) strengthened compared

to the gas phaseto the gas phase

5

Water dimers on Flat Metal SurfacesWater dimers on Flat Metal Surfaces

Gas Phase H2O Dimer:

Yellow = Yellow = --Blue = +

-20 -15 0-10 -5

Blue +

20 15 010 5E - EHOMO (eV)

A. Michaelides, Faraday Disc. 136, 287 (2007)

Water dimers on Flat Metal Surfaces

Strong H2O-metal bond and weak H

Strong H bond acceptor and weak

Water dimers on Flat Metal Surfaces

bond and weak H bond acceptor

acceptor and weak H2O-metal bond

“…Since the 1b1 orbitals are involved in water-metal bonding and in accepting H bonds, there is a competition between

l b di d h f H b d ”water-metal bonding and the acceptance of H bonds.”

S h t! A th i li ti ??So what! Are there any implications??

A. Michaelides and K. Morgenstern, Nature Mater. 6, 597 (2007)

6

STM Clustering and Diffusion at 40 K (Miquel Salmeron)STM Clustering and Diffusion at 40 K (Miquel Salmeron)

diffusion coefficients at 40 K:diffusion coefficients at 40 K:•• monomer ~ 0.0023 Åmonomer ~ 0.0023 Å22/s/s Why do dimers diffuse faster

•• dimer > 50 Ådimer > 50 Å22/s/s•• trimer,trimer, tetramer ~ 1.02 Åtetramer ~ 1.02 Å22/s/s

than monomers ?

Mitsui, Rose, Fomin, Ogletree & Salmeron, Science 297, 1850 (2002)

Atoms and molecules are lazy and cleverAtoms and molecules are lazy and clever

7

( )Asymmetric Adsorption � ~Free rotation (<20 meV)

Facile donor-acceptor exchange tunneling (110 meV)

Dimer diffusion ~103 > monomer diffusion

Ranea, Michaelides, Ramirez, Verges, de Andres & King, Phys. Rev. Lett. 92, 136104 (2003)g g y ( )

Michaelides, Applied Physics A 85, 415 (2006)

Ranea, Michaelides, Ramirez, Verges, de Andres & King, Phys. Rev. Lett. 92, 136104 (2003)g g y ( )

Michaelides, Applied Physics A 85, 415 (2006)

8

Modern surface science and low temperature scanningModern surface science and low temperature scanning tunneling microscopy of ice nucleation…

H O/Pd(111): Quasi 2 DH O/Cu(110): 1 DH O/Cu & Ag (111): 0 D H2O/Pd(111): Quasi 2-DH2O/Cu(110): 1-DH2O/Cu & Ag (111): 0-D

44 x 44 nm17 x 17 nm 150 x 150 nm

T. Yamada, S. Tamamori, H. Okuyama, and T. Aruga, Phys. Rev. Lett. 96, 036105 (2006)

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

A. Michaelides and K. Morgenstern, Nature Mater. 6,

597 (2007) , ( )597 (2007)

Low temperature (~10 K) STM for H2O/D2O on Cu(111) and Ag(111)

(a) (b)

Optimised DFT structures for H2O/Cu(111) clusters

(a) (b)

10

(d)(c)

Å

(d)(c)

All clusters are related and based on the cyclic hexamer – “thesmallest particle of ice” - with waters at or close to atop sites

A. Michaelides and K. Morgenstern, Nature Mater. 6, 597 (2007)

9

Eads (eV/H2O) O-O (Å) O-M (Å)

2.76

H L

Eads (eV/H2O) O O (Å) O M (Å)

Cu(111)(Cu-Cu: 2.58 Å)

0.44 2.64/2.76 2.39/3.16

2 762 76

2.64 2.64

H

H L

LAg(111)

(Ag-Ag: 2.93 Å)

0.41 2.66/2.75 2.66/3.21

2.64

2.762.76H L Does DFT PBE describe this effect reliably?

Approach�

E (eV)

�EBUCKLED-FLAT/Cu

0.76 Å

Approach�

E (eV)

PBE (Cu10 Cluster, AE) 1.05a

PBE0 (Cu10 Cluster, AE) 1.04a

MP2 (Cu10 Cluster, AE) 1.12b

(a) 6-311++G(3df,3pd) (b) 6-311++G(2df,pd)

A Michaelides Faraday Disc 136 287 (2007)A. Michaelides, Faraday Disc. 136, 287 (2007)

“There is a competition between water-water bonding and water-metal bonding.”

Strong H2O-metal bond and weak H

Strong H bond acceptor and weak

bond acceptorp

H2O-metal bond

“…Since the 1b1 orbitals are involved in water-metal bonding and in accepting H bonds, there is a competition between

water metal bonding and the acceptance of H bonds ”water-metal bonding and the acceptance of H bonds.

A. Michaelides and K. Morgenstern, Nature Mater. 6, 597 (2007)

10

Modern surface science and low temperature scanningModern surface science and low temperature scanning tunneling microscopy of ice nucleation…

H O/Pd(111): Quasi 2 DH O/Cu(110): 1 DH O/Cu & Ag (111): 0 D H2O/Pd(111): Quasi 2-DH2O/Cu(110): 1-DH2O/Cu & Ag (111): 0-D

44 x 44 nm17 x 17 nm 150 x 150 nm

T. Yamada, S. Tamamori, H. Okuyama, and T. Aruga, Phys. Rev. Lett. 96, 036105 (2006)

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

A. Michaelides and K. Morgenstern, Nature Mater. 6,

597 (2007) , ( )597 (2007)

A N M d l f I G h i T Di iA New Model for Ice Growth in Two Dimensions

17 x 17 nm

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

11

A N M d l f I G h i T Di i

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

STM Experiment DFT Model

A New Model for Ice Growth in Two Dimensions

STM Simulation

(41x53 Å)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

12

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

13

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

14

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

15

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

16

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

B ildi N I h t tiBuilding Nano-Ice, one hexagon at a time

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

J. Cerda et al., Phys. Rev. Lett. 93, 116101 (2004)

17

General Statements what we’ve discussed for water/metal interfaces

• Water monomers bind to atop sites and sit almost parallel to the surface

• Water clustering is favoured and readily occurs

General Statements, what we ve discussed for water/metal interfaces…

Water clustering is favoured and readily occurs

• A specific competition between water-metal bonding and the acceptance of H

bonds exists

• Hexameric building blocks play a key role in extended water/ice structures...

• Quantum nuclear effects (tunnelling) can be important to diffusion at low

temperatures

…what I’ve not mentioned and what we’d like to know more about…

• More about quantum nuclear effects

• Reliable quantitative prediction of adsorption energies (bond strengths)

• More about the role of the substrate structure: reactivity, symmetry, and lattice

constant

•....

Ice Nucleation:Ice Nucleation:���� Ice Nucleation:Ice Nucleation:Without impurities

water can become

��� (Kaolinite)���: Kaolinite

very cold(001)

Common ice

nucleating agents &

their “ice nucleation

200nm500nm

their ice nucleation

threshold”

• Clays: -5 to -12 °C

• AgI:-3 to -6 °C

• Metals, Metal oxides: eta s, eta o des

-5 to -12 °C

• Cholesterol = -1 to -2 °C

18

�� Ice Nucleation:Ice Nucleation:���: Kaolinite Ice Nucleation:Ice Nucleation:

Without impurities water can become

(001) very cold

200nm500nm

top

Common ice nucleating agents & their “ice nucleation

side

bottom

their ice nucleation threshold”

• Clays: -5 to -12 °C

• AgI:-3 to -6 °C

• Metals, Metal oxides: eta s, eta o des

-5 to -12 °C

• Cholesterol = -1 to -2 °C

Water on the hydroxyl terminated (001) surface of kaoliniteWater on the hydroxyl-terminated (001) surface of kaolinite

1 ML = 1H2O per OH2 p

1 eV ~ 100 kj/mol

19

Water monomer adsorptionWater monomer adsorption

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

D. Tunega, et al., J. Phys. Chem. B 108, 5930 (2004)

Water cluster adsorptionWater cluster adsorption

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

X. L. Hu and A. Michaelides, Surf. Sci. 602, 960 (2008)

20

2D overlayer adsorption2D overlayer adsorption

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

H down overlayer on Pt(111): H. Ogasawara et al., Phys. Rev. Lett. 89, 276102 (2002)

2D overlayer adsorption2D overlayer adsorption

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

H down overlayer on Pt(111): H. Ogasawara et al., Phys. Rev. Lett. 89, 276102 (2002)

21

Multilayer adsorptionMultilayer adsorption

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

H2O/Pt(111): G.A. Kimmel et al., Phys. Rev. Lett. 95, 166102 (2005)

Water on the hydroxyl terminated (001) surface of kaolinite

• Water monomers bind strongly

Cl t i i t f d ( t bl

Water on the hydroxyl-terminated (001) surface of kaolinite

• Clustering is not favoured (stable

clusters have not been identified)

• A 2D ice-like overlayer equally ce e o e aye equa y

stable to ice has been identified

• The water covered kaolinite

surface is itself hydrophobicsurface is itself hydrophobic

• A good lattice match is not the key

to ice nucleation on kaolinite

• Amphoteric hydroxyl groups play a major role in the chemistry of this interfaceinterface

X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)

X. L. Hu and A. Michaelides, Surf. Sci. 602, 960 (2008)

22

Conclusions XIAOLIANG

• Water monomers bind to atop sites and sit

almost parallel to the surfaceBO

LIMIN

BISWAJIT

JAVI

JIE

JIRI

• Water clustering is favoured and readily

occurs

f

BOANNA

JIRI

• A specific competition between water-metal

bonding and the acceptance of H bonds exists

• Hexameric building blocks are central toHexameric building blocks are central to

extended structures observed...

• Quantum nuclear effects (tunnelling) can be

important to diffusion at low temperatures

• At hydroxylated surfaces things can be quite

diff t K li it t l t i ddifferent, e.g. Kaolinite: water clustering does

not appear to be favoured but a stable 2D ice-

like overlayer is predictedf / i

like overlayer is predicted www.esf.org/euryi

23