Conformation-family Monte Carlo: A new method for crystal structure prediction

A new global optimization method, Conformation-family Monte Carlo, has been developed recently for searching the conformational space of macromolecule s. In the present paper, we adapted this method for prediction of crystal s tructures of organic molecules without assuming any symmetry constraints ex cept the number of molecules in the unit cell. This method maintains a data base of low energy structures that are clustered into families. The structu res in this database are improved iteratively by a Metropolis-type Monte Ca rlo procedure together with energy minimization, in which the search is bia sed toward the regions of the lowest energy families. The Conformation-fami ly Monte Carlo method is applied to a set of nine rigid and flexible organi c molecules by using two popular force fields, AMBER and W99. The method pe rformed well for the rigid molecules and reasonably well for the molecules with torsional degrees of freedom.