DEVELOPMENT OF A POTENTIAL FUNCTION FOR DESCRIBING THE PROPERTIES OF HCN CLUSTERS

We developed potential functions for (HCN)(2) and used them to study l arger aggregates. The functions are based on ab initio perturbation ca lculations for the dimer and on molecular properties also estimated fr om ab initio calculations involving two different basis sets. The over all energy is resolved into electrostatic, repulsion, induction, and d ispersion components. The electrostatic contribution is represented by a multipole expansion at several sites. The repulsion function is of the exponential type and includes atomic anisotropy. The dispersion is described by means of a London-type formula. Finally, the induction c ontribution is expressed in terms on polarizabilities distributed amon g the atoms. The proposed functions accurately reproduce the character istics of the HCN dimer and the two minimum-energy forms of the trimer . Also, they predict various properties (e.g., the dependence-of the d ipole moment and interaction energy on cluster size) of larger aggrega tes. (C) 1998 American Institute of Physics.