Abstract

It is an obvious goal for a full theory of the solid state to enable the prediction of 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 avoided. I will present a strikingly simple and effective approach to the unbiased prediction of crystal structures. It 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. More complex structures can be discovered by a judicious application of constraints to the search space. I will illustrate the use of this technique with applications to situations which present considerable experimental challenges. This will include hydrogen, ammonia and lithium at high pressures.