Derivation of a new force field for crystal-structure prediction using global optimization: Nonbonded potential parameters for hydrocarbons and alcohols

A new procedure has been developed for deriving accurate nonbonded potential parameters for crystal-structure prediction. The method consists of two steps. First, an initial set of potential parameters is derived by fitting to ab initio interaction energies of dimers. Second, this initial set is refined to satisfy the following criteria: the parameters should reproduce the observed crystal structures and sublimation enthalpies accurately; the observed crystal structure should correspond to the global or to one of the lowest-energy minima of the potential. These goals are achieved by applying our new global optimization-based method for deriving nonbonded potential parameters (J. Phys. Chem. B 2003, 107, 712), which consists of a force-minimization and a vector Monte Carlo [VMC] method, to information about the potential energy surface of the crystal. The procedure enables one to obtain the best possible set of parameters for crystal-structure prediction for a given form of the potential. The computed nonbonded parameters of the "6-exp-1" potential, derived by using the new procedure, are presented for aliphatic and aromatic hydrocarbons and alcohols.