The challenge of molecular crystal structure prediction
Garnet Chan gave a nice talk at the Condensed Phase Dynamics meeting about recent work on the problem of using computational methods to predict the crystal structure of organic molecular crystals. He began with the provocative statement of John Maddox , long-time editor of Nature, that One of the continuing scandals in the physical sciences is that it remains impossible to predict the structure of even the simplest crystalline solids from a knowledge of their composition. I previously posted about this "scandal". Molecular crystals are particularly challenging because they often form polymorphs , i.e. several distinct competing crystal structures, that have energies differing on the scale of 1 kJ/mol [0.2 kcal/mol ~ 10 meV]. Calculating the absolute and relative energies of different crystal structures to this level of accuracy is a formidable challenge, going far beyond what is realistic with most electronic structure methods, such as those based on Density Function