High pressure physics - a gift to theory

Of all the thermodynamic variables, our theoretical methods have the greatest control over pressure. The foundation of modern density functional based total energy methods rests on early studies on the behaviour of crystals under pressure. High pressure experiments are, however, far from straightforward. These experiments typically involve only small quantities of the sample of interest.  Analysis is difficult, and frequently incomplete. I will discuss how modern structure prediction methods (and Ab Initio Random Structure Searching[1,2] in particular) have revolutionised the study of dense matter. The ability to make reasonable predictions of crystal structures has enabled puzzling experiments to be interpreted, and also provided suggestions for what might be just out of reach. Examples include "mixed" phases in dense hydrogen [3] (now identified as Phase IV[4]), the decomposition of water at the pressures encountered in gas giant planets,[5] and four new thermodynamically stable phases of carbon on the way to stellar pressures.[6]

[1] Chris J. Pickard, and R. J. Needs. "High-pressure phases of silane." Physical Review Letters 97, no. 4 (2006): 045504.
[2] Chris J. Pickard, and R. J. Needs. "Ab initio random structure searching." Journal of Physics: Condensed Matter 23, no. 5 (2011): 053201.
[3] Chris J. Pickard, and Richard J. Needs. "Structure of phase III of solid hydrogen." Nature Physics 3, no. 7 (2007): 473-476.
[4] Chris J. Pickard, Miguel Martinez-Canales, and Richard J. Needs. "Density functional theory study of phase IV of solid hydrogen." Physical Review B 85, no. 21 (2012): 214114.
[5] Chris J. Pickard, Miguel Martinez-Canales, and Richard J. Needs. "Decomposition and terapascal phases of water ice." Physical Review Letters 110, no. 24 (2013): 245701.
[6] Miguel, Martinez-Canales Chris J. Pickard, and Richard J. Needs. "Thermodynamically stable phases of carbon at multiterapascal pressures." Physical Review Letters 108, no. 4 (2012): 045704.
Bio: Chris Pickard is the inaugural Sir Alan Cottrell Professor of Materials Science in the Department of Materials Science and Metallurgy, University of Cambridge. Previously he was Professor of Physics, University College London (2009-2015), and Reader in Physics, University of St Andrews (2006-2008). He has held both EPSRC Advanced and Leadership Research Fellowships, and is currently a Royal Society Wolfson Research Merit Award holder (2015). He is a lead developer of the widely used CASTEP code, and introduced both the GIPAW approach to the prediction of magnetic resonance parameters and Ab Initio Random Structure Searching. In 2015 he won the Rayleigh Medal and Prize of the Institute of Physics.

http://www.msm.cam.ac.uk/department/profiles/portrait/Pickard.jpg