MSc in High Performance Computing:
Guest Lecture 21/1/2011
Applications of HPC
to
Materials Chemistry
Research Highlights Of The
Materials Chemistry Consortium (e05)
Scott.Woodley@ucl.ac.uk
http://www.ucl.ac.uk/klmc/mcc
Strategic Vision Statement
The HPC Materials Chemistry Consortium exploits the latest developments in HPC
technologies, in a wide ranging programme of development, optimisation and
applications studies aimed at modelling and predicting the structures, properties and
reactivities of functional materials, including catalysts, ceramics, minerals and
molecular materials. The programme embraces both large scale simulations based on
force-fields and electronic structure techniques employing both Density Functional
Theory, Hartree Fock and hybrid techniques. Strong emphasis is placed on code
development and optimisation for MPP platforms while several applications highlight
systems of industrial importance. There is strong symbiosis between the modelling
studies of the consortium and experimental programmes.
Consortium Members*
 Prof Richard Catlow, Dr Samuel A. French, Mr Said Hamad, Dr Erika J Palin, Dr Alexey A Sokol, Miss Eleonora Spano‚ Ms Judy To, Mr Dan Wilson,
Dr Scott M Woodley
 Prof Nicholas M Harrison, Mr Amit Agarwal, Dr Ian J. Bush, Miss Jennifer A Chan, Dr. Xiao-Bing Feng, Mr Matthew Habgood, Dr Giuseppe Mallia,
Dr Barbara Montanari, Dr. Sanghamitra Mukhopadhyay, Ms Jessica J Scaranto, Dr Barry G Searle
 Dr Ben Slater, Ms Kat F Austen, Ms Dervishe Salih
 Dr Emilio Artacho, Dr Miguel Pruneda, Mr Jon Wakelin, Mr Andrew D Walkingshaw, Dr. Toby O H White
 Dr Fernando Bresme, Mr Luis Gomez Camara, Dr Minerva Gonzalez, Mr Kafui K Tay
 Prof Julian Clarke, Dr Steven Y Liem, Ms Beatrice Nikolaidi
 Dr Martin T Dove, Dr Mark Calleja, Dr Guillaume Ferlat, Miss Marivi Fernandez-Serra, Dr Ilian T. Todorov, Dr Kostya Trachenko
 Prof Julian D. Gale
 Prof Michael Gillan, Dr Dario Alfe, Dr. Maria Alfredsson, Dr Louise Dash
 Prof John Harding, Dr Dorothy M Duffy, Dr Duncan J Harris
 Dr Saiful Islam, Dr Julian R Tolchard
 Dr Lev Kantorovich, Mr Chris L Hobbs, Mr Ross E A Kelly, Dr Natalia Martsinovich, Mr Thomas P Trevethan
 Prof Moti Lal, Bill Smith, Dr Martin Plummer
 Dr Nora H. de Leeuw , Mr Ricardo Grau-Crespo, Dr Antonio Tilocca
 Dr Phil P Lindan, Dr Elena Bichoutskaia, Miss Elizabeth J Duplock, Miss Samantha Lister, Dr Changjun C Zhang
 Dr William W C Mackrodt
 Prof Steve Parker, Mr David DJ Cooke, Mr Sebastien SN Kerisit, Dr Arnaud Marmier, Mr Dino Spagnoli
 Prof N Quirke, Dr David Cubero, Mr Antoni Homs-Corbera
 Prof Mark PM Rodger, Mr Robert Hawtin, Dr Changman Moon
 Prof Sasha Shluger, Mr Andrey Y Gal, Dr Jacob L. Gavartin, Dr David Munoz Ramo, Ms Dervishe Salih, Dr. Peter P.V. Sushko, Dr Matthew B
Watkins
 Dr Graeme W Watson, Miss Joanne Fearon, Dr. Michael J Nolan
 Dr David J Willock, Mr Rudy Coquet, Mr Edward Jeffery
 Dr Kate Wright, Mr Andrew M Walker Dr Stephen S A Wells
* Registered on either HPCx or CSAR
Consortium Members*
Prof Richard Catlow, Chemistry, University College London
Dr Dorothy Duffy, Physics, University College London
Miss Xin Xia, Dr Gargi Dutta, Mr Alastair Smith, Mr Ludovic Briquet,
Miss Martina Miskufova, Dr Alexey A Sokol, Dr Aron Walsh, Miss Hsin-Yi
Tiffany Chen, Mr Crispin S Cooper, Miss Elisabeth Krizek
Mr Jack Mulroue
Prof Nic Harrison, Chemistry, Imperial College London
Dr Giuseppe Mallia, Dr Leandro Liborio, Dr. Sanghamitra Mukhopadhyay,
Dr Leonardo Bernasconi, Dr Ruth Martinez-Casado,
Mr Ehsan A Ahmad, Miss Su Chuen Chew, Miss Romi Kaur
Dr Ricardo Grau Crespo, Chemistry, University College London
Prof Claire Grey, Chemistry, University of Cambridge
Dr Derek S Middlemiss
Prof Roy L. Johnston, Chemistry, University of Birmingham
Mr. Lauro Oliver Paz Borbon
Prof M Saiful Islam, Chemistry, University of Bath
Prof Lev Kantorovich, Physics, Kings College London
Dr Pooja Panchmatia, Dr Corinne Arrouvel, Mr Paul J Weaver, Mr Jesse Dufton,
Dr Chris Eames, Mr Grahame R Gardiner
Miss Manuela M Mura, Mr Dawid D Toton, Mr Joseph Bamidele
Prof Nora de Leeuw, Chemistry, University College London
Mr Anthony J Devey, Mr Thomas D Daff, Miss Emilia Tang, Dr Devis Di Tommaso,
Dr Iman Saadoune, Ms Neyvis Almora Barrios, Dr Zhimei Du, Dr Hasani HR Chauke,
Dr Simona Irrera, Dr Ian Streeter, Miss Saima Haider, Dr Glenn Jones, Dr Mariette M
Wolthers, Mr Richard I Ainsworth, Alberto A Roldan-Martinez, Mr Nelson Y Dzade
Kostya Trachenko, Physics, Queen Mary London
Prof Angelos Michaelides, Chemistry, University College London
Mr Xiaoliang Hu, Mr Jiri Klimes, Dr Limin Liu Liu, Mr Ding Pan, Mr Erlend Davidson,
Dr Brent G Walker, Dr Xinzheng Li
Dr Barbara Montanari, Daresbury Laboratory
Prof Alex Shluger, Physics, University College London
Miss Christine L Bailey, Mr Naunidh S Virk
Dr Keith P McKenna, Dr David Munoz Ramo, Dr Matthew B Watkins, Mr Matthew Wolf,
Dr Gilberto Teobaldi,Dr Niri Govind, Miss Natalie N C Moore, Dr Thomas Trevethan
Dr Arash A Mostofi, Materials and Physics, Imperial College London
Dr Ben Slater, Chemistry, University College London
Prof Stephen Parker, Chemistry, University of Bath
Mr Iain A Bethune, Mr Raimondas Galvelis, Mr Florian Schiffmann, Mr Zamaan Raza
Mr Wojciech Gren, Mr Jeremy P Allen, Mr Tom V Shapley, Dr Marco Molinari
Dr David J Willock, Chemistry, University of Cardiff
Dr Martin M Plummer, Daresbury Laboratory
Mr Adam Thetford, Miss Kara Howard, Mr Christopher A Lee
Dr Paul Popelier, Chemistry, University of Manchester
Prof John Harding, Materials, University of Sheffield
Dr Majeed S Shaik, Dr Yongna Yuan, Mr Matthew J Mills
Dr Colin C L Freeman, Mr Hung-Ru Chen
Dr Peter Sushko, Physics, University College London
Dr Jochen Blumberger, Physics, University College London
Mr Clyde JA Fare, Dr Anna Kimmel, Dr Antonio AT Torrisi
Mr Marian Breuer
Dr Antonio Tilocca, Chemistry, University College London
Dr George Darling, Chemistry, University of Liverpool
Dr Jamieson Christie
Dr Matthew S Dyer, Miss Kim Jelfs, Dr Jeremy Rabone, Mr Geoff Thomas,
Mr Christopher M Collins, Dr Abbie E Trewin
Dr Scott M Woodley, Chemistry, University College London
Prof Martin Dove, Earth Sciences, University of Cambridge
Dr Helen F Chappell
Mr Fabiano Corsetti
Dr Asimina AM Maniopoulou, Mr Russell Woolley, Dr Andrew R Turner,
Mr Mohamed K Matar, Dr Regina R Maphanga
Dr Martinus A Zwijnenburg, Chemistry, University College London
* Registered on HECToR
Management of Resources
All-day meeting held every six months
Key points:
Morning devoted to talks (on research and HPC issues) by members who were allocated
major HPC-time for the last six months, as well as ocasional guest speakers.
HPC-time proposals for the next 6 months distributed among members > 1 week beforehand.
Interim proposals are considered outside meetings for smaller HPC requests.
Open management system
As well as using email for collecting/distributing information, key information is stored on
our website http://www.ucl.ac.uk/klmc/mcc
Information includes:
All sub-project proposals,
Allocation and usage reports (by user, sub-group, sub-project and theme),
Highlights of our research, list and photographs of members,
Notes for new users, Final Report to EPSRC,
Minutes of our meetings.
One day seminars
E.g. workshop for new and experienced users of relevant codes utilised by consortium
The Seven Themes
Surfaces and Interfaces
Biomaterials
Materials for Power
Nano and Defect Chemistry
Reactivity
Environmental Materials
Quantum Devices
Reactivity
Publication on Website
text removed
Nano and Defects
Publication on Website
text removed
Surfaces and Interfaces
Publication on Website
text removed
Materials for energy technology
Publication on Website
text removed
Biomaterials Environmental Materials
Publication on Website
text removed
Publication on Website
text removed
Key Research Highlights (1)
The first theoretical study of the influence of polymer weight, tacticity and conformation on inhibitor
activity, which also showed that kinetic inhibitors can actually promote nanocrystal growth
RW Hawtin, PM Rodger, J. Mater. Chem. 16 1934 (2006)
Development of a comprehensive model of the first thermally stable inorganic electride based on the
complex oxide 12CaO.7Al2O3, which can be used in a variety of applications such as a cold electron
emitter and as an effective reducing agent in catalysis
PV Sushko, AL Shluger, M Hirano, H Hosono, J. Am. Chem. Soc. 129 942 (2007)
Development of a new microscopic interpretation of the origin of the hydration force, which is connected
to the anomalous dielectric behaviour of water under confinement conditions
J Faraudo, F Bresme, Phys Rev. Lett. 7 94 (2005)
The elucidation by dynamical simulations of the mechanisms of pre-nucleation in crystal growth of both
inorganic and molecular materials; pre-nucleation phenomena can control the polymorphic outcome in
crystallisation.
ZnS: S Hamad, S Cristol, CRA Catlow, J. Amer. Chem. Soc. 127 2580 (2005)
5-fluoruracil: S Hamad, C Moon, CRA Catlow, AT Hulme, SL Price, J. Phys. Chem. B 110 3323 (2006)
Determination of the electronic and magnetic structure of the partial oxidation catalyst FeSbO4 and of the
relevant redox processes, as a function of surface composition and chemical potential
R Grau Crespo, CRA Catlow, NH de Leeuw, J. Catal. 248 77 (2007)
The blind structure prediction of the new ice XIV phase
GA Tribello, B Slater, CG Salzmann, J. Amer. Chem. Soc. 128 12594 (2006)
Key Research Highlights (2)
Demonstration that graphitic ribbons support very long-range ferromagnetic interactions and
are thus of great interest for spintronics applications
L Pisani, JA Chan, B Montanari, NM Harrison, Phys. Rev. B 75 064418 (2007)
On investigating an archetypal interface formed by the LaAlO3 film growth on SrTiO3 (001)
surface, discovered that intermixing of all four metal species and formation of a quaternary
oxide region is energetically preferable to the interface. This finding calls for a rethink of the
origin of the two-dimensional electron gas associated with this interface.
L Qiao, TC Droubay, V Shutthanandan, Z Zhu, PV Sushko, SA Chambers,
J Phys: Condense Matter 22, 312201 (2010)
Employed ab initio simulations to create the first atomic-scale model of stoichio-metric and
oxygen deficient novel oxide 12CaO.7Al2O3, which has intriguing properties and is
promising for applications in chemistry and electronics.
PV Sushko, AL Shluger, Y Toda, M Hirano, H Hosono, Proc. R. Soc. A, in press.
State-of-the-art DFT calculations with self-consistent incorporation of the van der Waals
(vdW) interaction explained the existing controversy concerning a flat surface potential on
the one hand and strong binding of flat organic molecules to the Au(111) surface on the
other.
M Mura, A Gulans, T Thonhauser, L Kantorovich, Phys. Chem. Chem. Phys. 12 4759 (2010)
Surfaces and Interfaces
Influence of pH on crystal growth of silica
Steve Parker, Chemistry, University of Bath
Ice formation on surfaces and in the upper atmosphere
Angelos Michaelides, LCN, University College London
Influence of pH on crystal growth of silica
Steve Parker, Chemistry, University of Bath
Publication on Website
Slides Removed
Nanoscale water film on salt
Large scale ab initio molecular dynamics simulations of liquid solid
interfaces: e.g. a nanoscale water film on salt:
For more information see: www.chem.ucl.ac.uk/ice
Liu et al. J. Am. Chem. Soc. 130, 8572 (2008)
The smallest particle of ice
imaged with STM and DFT
For more information see: www.chem.ucl.ac.uk/ice
Michaelides and Morgenstern, Nature Mater. 6, 597 (2007)
Upper atmosphere - Ice formation
高岭石: Kaolinite
Ice Nucleation:
Without impurities
water can become
very cold
(001)
500nm
200nm
Common ice
nucleating agents &
their “ice nucleation
threshold”
top
side
bottom
• Clays: -5 to -12 °C
• AgI:-3 to -6 °C
• Metals, Metal oxides:
-5 to -12 °C
• Cholesterol = -1 to -2 °C
Ice formation in the upper atmosphere
First principles
calculations predict
the formation of a
2D ice-like overlayer that is equally
stable to bulk ice.
0
1/6 1/3
1/2 3/4
5/6
1
7/6
3/2
Coverage
X. L. Hu and A. Michaelides, Surf. Sci. 601, 5378 (2007)
X. L. Hu and A. Michaelides, Surf. Sci. 602, 960 (2008)
The surface of proton disordered ice Ih
The surface of proton disordered ice Ih is proton ordered
a first principles prediction.
Electrostatic repulsion between protons at the surface cause them to line up,
effectively making the surface superchilled. This insight into the ice surface is
likely to have implications for the equilibrium crystal shape of ice crystals or
catalytic reactions which take place on their surfaces.
Pan et al. Phys. Rev. Lett. 101, 155709 (2008)
Wetting layer structures
To wet or not to wet:
Dispersion forces tip the balance for water-ice on metals
Standard density functionals
predict that water-ice should
not wet metals,
but form 3 dimensional nonwetting ice crystals.
Accounting for dispersion
forces rectifies this
problem.
Results agree with
experiment.
water on Cu(110):
most well-characterized
water on Ru(0001)
most widely investigated
For more information see: www.chem.ucl.ac.uk/ice
Carrasco et al. Phys. Rev. Lett. 106, 126101 (2011)
Materials for energy technology
Solid oxide fuel cells, Cathode and Anode Materials
Saiful Islam, Chemistry, University of Bath
Hydrogen Storage Materials: MgH2
Ricardo Grau-Crespo, Chemistry, University College London
Cathode Materials
Claire Grey, Chemistry, University of Cambridge
Solid Oxide Fuel Cells
SOFC
Space
heater
Energy conversion device – local heat & power generation
New or improved materials are key to major advances
Fuel Cell: Novel Ionic Conductor
LaBaGaO4
Is a good O2- conductor
Has complex structure
with tetrahedral Ga
- Conduction mechanism?
- MD/atomistic simulations
GaO4
La
Ba
LaBaGaO4 : Conduction Mechanism?
•
Unusual co-operative mechanism
 breaking and re-forming Ga2O7
from neighbouring GaO4 units
•
Ga2O7
Flexible structure
GaO4
•
Related oxides with tetrahedra?
Nature Mater. 6, 871 (2007)
Cathode and Anode Materials
Saiful Islam, Chemistry, University of Bath
Publication on Website
Slides Removed
Hydrogen Storage Materials: MgH2
Ricardo Grau-Crespo, Chemistry, University College London
Publication on Website
Slides Removed
Cathode Materials
Claire Grey, Chemistry, University of Cambridge
Publication on Website
Slides Removed
Quantum Devices
Sc Spin Qubits in Carbon Peapods
Barbara Montanari, University of Oxford & Daresbury Lab
Lifting the C60 Molecule with a SPM Tip
Lev N. Kantorovich, Physics, King’s College London
Charge Rearrangement in Peapods
L Ge, B Montanari, J Jefferson et al PRB 77 235416 2008
J Warner, A Watt, L Ge, Nano Lett 8 (4) 1005 2008
How Spin Qubits Align in Peapods
Lifting the C60 Molecule with a SPM Tip
Using only the chemical tip-molecule interaction
C60 in a stable
adsorption
configuration
C60 at a pivoting
point
(2 Si-C bonds)
lift
next stable
adsorption
configuration
deposit
carry the C60
(attached only
to the tip)
 C60 can be lifted from the surface thanks to the tip-C60
chemical bonding, without applying bias voltage
 The C60 needs to be brought to a suitable adsorption
configuration (precursor state) with minimised bonding to
the substrate
 a combination of lateral and vertical manipulation
 The precursor mechanism may be generally valid for
vertical manipulation of adsorbates
0
-1
unsuccessful
Binding
energy, eV
Lateral
manipulation
successful
-2
-3
Barrier
2 eV
Tip height, Å
Environmental Materials
Radiation damage effects in nuclear and thermonuclear
power applications
Kostya Trachenko, Physics, Queen Mary, Martin Dove, Materials, Cambridge
Ilian Todorov, Daresbury Laboratory, Dorothy Duffy, Physics, UCL
Electronic effects in radiation damage simulations
Dorothy Duffy, LCN, University College London
Radiation damage effects in nuclear and thermonuclear
power applications
Kostya Trachenko, Physics, Queen Mary, Martin Dove, Materials, Cambridge
Ilian Todorov, Daresbury Laboratory, Dorothy Duffy, Physics, UCL
Publication on Website
Slides Removed
Electronic effects in radiation damage simulations
Dorothy Duffy, LCN, University College London
Publication on Website
Slides Removed
Reactivity
DFT+U applied to supported Au/Fe2O3 catalysts
Dave J Willock, Chemistry, Cardiff University
Challenges to Methanol Synthesis
Alexey Sokol, Richard Catlow, Gargi Dutta, Chemistry, UCL
DFT+U applied to supported Au/Fe2O3 catalysts
•
•
•
Experiments identified particles containing around 10
Au atoms as most active.1
Calculations show that dissociation of O2 is found to be
favourable at metal/oxide interface but not on an
isolated cluster.
Further experiments/calculations have shown these
catalysts may also break the CO bond.2
200
Au10
150
Energy / kJ mol-1
High activity
O2 gas
100
50
0
Au10 on Fe2O3
-50
-100
-150
-200
-250
-300
0
0.5
1
1.5
2
2.5
3
3.5
4
O...O / Å
4.5
1. G. Hutchings, C. Kiely et al., Science, 2008, 321, 1331
2. G. Hutchings, D.J. Willock et al.,
Phys. Chem. Chem. Phys., 2011, Advanced Article,
DOI: 10.1039/C0CP01852J.
ZnO (000-1)-O
ZnO (0001)-Zn
Surface hydrogenation
Methanol –
Catalytic cycle
Copper
anchoring
Identification of Vibrational Modes
AZn
BZn
1507cm-1
(BZn)
1745cm-1
(BO)
(AO)
(AZn)
SA French et al, J Chem Phys 118 (2003) 317
Zinc Hydride Vibrational Modes
Type I
̶
reversible
Zn – H
1745cm-1
expt. 1710cm-1
Type II
̶
irreversible
Zn – H
1507cm-1
expt. 1475cm-1
Surface Defects
Intrinsic surface vacancy traps electron
AA Sokol et al, Int J Quant Chem 99 (2004) 695
Challenges to Methanol Synthesis
Alexey Sokol, Richard Catlow, Gargi Dutta, Chemistry, UCL
Publication on Website
Some Slides Removed
Biomaterials
Peptide Influence on the (1 0 4) Calcite Surface
John Harding, Chemistry, University of Sheffield
Mark Rodger, Physics, University of Warwick
Interaction of Bio-molecules with Apatite Mineral Surfaces
Nora de Leeuw, Chemistry, UCL
Bio-inspired (Fe,Ni)S nano-catalysts for CO2 activation
Nora de Leeuw, Chemistry, UCL
Bio-inspired (Fe,Ni)S nano-catalysts for CO2 activation
Nora de Leeuw, Chemistry, UCL
Publication on Website
Slides Removed
Surface morphology - Influence of proteins
How do peptides
influence the
morphology of
calcite and the
(1 0 4) calcite
surface in water?
water
solution
Chosen peptides
mimic the proteins
in egg shells.
(1 0 4)
calcite
surface
peptide
MD simulations
Collagen Structure
c
Adsorption to hydroxy-apatite
Adsorption of
Proline
Hydroxyproline
Glycine
to hydroxy-apatite
SIESTA calculations
Glycine adsorption
(0001)
(1010)
H from –COOH group migrates to surface
OH, forming trapped water molecule
Proline adsorption
(0001)
(1010)
H from –COOH group migrates to -NH2
group then to surface PO4 group
Hydroxy-proline adsorption
(0001)
(1010)
H from –COOH group migrates to
surface PO4 group. Extra flexible
–OH group strengthens interactions
Adsorption of amino acids at HA surfaces
Adsorption energies (kJ mol-1)
HA Surface
Glycine
Proline
Hydroxyproline
(0 0 0 1)
-77.05
-70.58
-106.73
(0 1-1 0)
-359.92
-509.77
-609.79
All amino acids form multiple interactions with surface species,
particularly if they can bridge between two surface calcium ions
Physisorption to (0001) surface with few dangling bonds
Strong interactions with less stable (01.0) surface, involving
changes in chemical bonding
Glycine more flexible but less adhesive
Collagen should provide favourable nucleation sites for growth of
hydroxyapatite (01.0) surface
Nano and Defects
The electronic structure and properties of a novel
complex oxide 12CaO.7Al2O3
Peter Sushko, Alex Shluger, Physics, University College London
Structure Prediction and Optical Properties
of Doped Nanoparticles
Scott Woodley, Shephen Shevlin, Chemistry, University College London
The electronic structure and properties of a novel
complex oxide 12CaO.7Al2O3
Peter Sushko, Alex Shluger, Physics, University College London
Publication on Website
Some Slides Removed
Photoactive H-doped C12A7
UV light
H2 + O2–  H– + OH–
H–  H0 + e–
H0
H2
O2–
H0 + O2–  OH– + e–
O2–
O2–
K. Hayashi et al., Nature 419, 462, (2002)
Matsuishi et al., JACS, 127, 12454 (2005)
H–
O2–
OH–
e–
e–
P. V. Sushko et al., APL 86, 092101, (2005)
P. V. Sushko et al., PRB 73, 045120, (2006)
e–
Structure Prediction and Optical Properties
of Doped Nanoparticles
Scott Woodley, Shephen Shevlin, Chemistry, University College London
Publication on Website
Some Slides Removed
Photocatalyst
H2 production via heterolytic dissociation of water
H2O → H2 + ½O2
Titania (TiO2)n
Pros: Stable and non-toxic
Con: Band-gap rather large
3.03 eV for rutile
3.18 eV for anatase
only a small part of the solar spectrum can be harvested
Anion doping:
reduce the bandgap
increase photoactivity.
Smaller particles:
greater surface area
dopants closer to H2O
reduces HOMO-LUMO gap
Photocatalyst
6
7
LUMO+1
LUMO
HOMO
HOMO–1
10
HOMO residing solely on the O(2p) states
LUMO residing solely on the Ti(3d) states
Titania (TiO2)n
13
Photocatalyst
×
CO
×
NO
×
SO
6
6
10
10
×
CO
Doped Titania (TiO2)n
×
NO
×
SO
Photocatalyst
All of the dopants reduce the transition energy
×
CO
6
10
×
NO
×
SO
LUMO
HOMO
carbon and sulphur dopants
nitrogen-doping
transition energies that are close to the peak in the solar spectrum (~2.5 eV)
transition energy that is too low (~ 1.0 eV) for water-splitting applications
thus are more efficient at photoconversion than undoped nanoparticles.
2010
13-17
Acknowledgements
HPC Materials Chemistry Consortium
Funded by EPSRC
Lead by Richard Catlow
Driven by
HECToR
All Members of the
HPC Material Chemistry Consortium
Publications
Journal of Materials Chemistry 2006 (vol.16 iss. 20)
Royal Society Proc A 2011(in press)
Scott.Woodley@ucl.ac.uk