Ab Initio Random Structure Searching: exploring structure space with random numbers

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• Prof Chris J. Pickard, UCL
• Thursday 01 October 2009, 14:00-15:00
• Theory Library.

If you have a question about this talk, please contact Dr Dimitri M Gangardt.

It is an obvious goal for a complete theory of the solid state to be able to reliably predict the structures adopted by large collections of atoms under a variety of conditions, including high pressure. But until relatively recently it is one that has been largely unrealised, with the first useful first principles approaches emerging only in 2006. I will present a strikingly simple and effective approach to the unbiased prediction of crystal structures. Ab initio random structure searching (AIRSS) is based on an initial uniform random sampling of the space of possible structures, followed by robust structural optimisation to the local enthalpy minimum of each initial structure under quantum mechanical (density functional theory) forces and stresses.[1] More complex structures can be discovered by a judicious application of constraints to the search space. It can also be used as tool for solving crystal structures that have resisted standard experimental techniques.

Applications include the phase III of hydrogen², ionic ammonia as ammonium amide³ and lithium, an elemental electride.[4]

[1] C.J. Pickard and R.J. Needs, Phys. Rev. Lett. 2006, 97, 45504 [2] C.J. Pickard and R.J. Needs, Nature Physics 2007, 3, 473-476 [3] C.J. Pickard and R.J. Needs, Nature Materials 2008, 7, 775-779 [4] C.J. Pickard and R.J. Needs, Phys. Rev. Lett. 2009, 102, 146401

This talk is part of the Theoretical Physics Seminars series.

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