An analytical representation of the model potential for beryllium trimers

A 2- and 3-body model potential for the Be3 cluster has been constructed. The parameters of the 2- and 3-body terms were fitted separately to the corresponding ab initio many-body energies calculated at the MP4 level. The study of the 3-body component in different triangle conformations reveals that the 3-body forces determine the magnitude of the interaction energy in a relatively large region of distances and angles. The analysis of exchange and dispersion contributions makes it possible to elucidate the nature of binding in the Be3 cluster.