Prediction of crystal structures of organic molecules

We have developed a new algorithm for crystal structure prediction that takes a conformer of an organic molecule and produces a number of candidates of crystal structures for this molecule, together with a score that roughly approximates the energy of the respective crystal structure. The prediction method takes steric aspects (dense packing) as well as chemical interactions into account. The algorithm differs from existing methods in three aspects. First, we analyse a single molecule rather than a collection of identical molecules. The analysis yields candidates for symmetry operations that are suitable for making the crystal. Each of the candidates is generated by a chemical interaction between two versions of the molecule. Second, we model space discretely, currently as a mesh with size 1 Angstrom. Third, the scoring function representing energy is derived statistically from known crystal structures and tabulated. Our program FlexCryst computes a list of crystal structures ranked according to our scoring function. The new algorithm is currently implemented for the four space groups P1, <P(1)over bar>, P2(1), and P2(1)2(1)2(1). The three latter space groups are widespread in nature. The algorithm computes structural models of acceptable quality and shows excellent time performance. (C) 1998 Elsevier Science B.V. All rights reserved.