Chapter 5 - Crystal structure prediction from molecular structure: Highlights and shadows

Abstract

Abstract A set of laws of crystal packing are presented, as concerns hydrogen bonding, close packing, space group and symmetry element presence and molecular shape. Racemic vs chiral crystallization is examined with Wallach's rule. Some principles of computational crystal structure prediction (CSP) are summarized, concerning search and ranking of possible structures. Results of a simple algorithm based on successive application of symmetries, developed almost 30 years ago, are presented and compared with more sophisticated approaches. The history and development of the Cambridge crystal structure prediction blind tests is discussed, and the results of the six tests so far conducted are analyzed in detail. A critical survey is given of the relative performance of several methods also in connection with the relative costs. A final consideration is given to the objective obstacles that stand in the way of CSP, concerning the intrinsic accuracy of force fields, free energies, thermal libration, and the often encountered serendipity of the experimental polymorph search science.