NONADDITIVE FORCES IN ATOMIC CLUSTERS - THE CASE OF AGN

The closed recurrence formula which expresses the energy of m-body int eractions through the energies of 2-, 3- and (m- 1)-body ones is obtai ned. The m-body contributions to the interaction energy of silver clus ters are calculated by the all-electron non-local spin density method. The importance of not only 3- but also 4- and 5-body forces for clust er stability has been revealed. The stable geometry of planar and spat ial silver clusters is determined by the competition of attractive add itive forces and repulsive non-additive forces. The larger magnitude o f non-additive forces for three-dimensional conformations in compariso n with two-dimensional ones is the reason that for Ag(n) with n = 4-6 the most stable geometries are planar.