Nonadditive three-body interactions of rare-gas atoms. I. Small and intermediate distances

Nonadditive three-body interaction energies are calculated for He₃, Ne₃, Ar₃, and Kr₃. The electron density of the total system of three atoms is assumed to be equal to the sum of the three separate atomic electron densities, and the energy is evaluated from this assumed density using an electron-gas energy formula in terms of local electron density. The results show that the three-body contributions to the interaction energy for these systems is very small, usually less than a few percent of the sum of the pair forces, over a large range of internuclear separations.