Vibrationally excited states and fragmentation geometries of Ne-N and Ar-Nclusters, N=3-6, using hyperspherical coordinates

We calculate the ground state and a class of zero orbital angular momentum (L=0) vibrationally excited state energies for Ne-N and Ar-N clusters using an adiabatic hyperspherical representation to solve the nuclear Schrodinge r equation. The Schrodinger equation in the hyperangular coordinates is sol ved for a sequence of fixed hyperradii by diffusion Monte Carlo techniques, which determines the lowest effective potential curve. We monitor structur al properties such as the pair and angle distribution as a function of the hyperspherical radius. These structural studies allow us to identify config urational changes as the N atom cluster fragments into an (N-1)-atom cluste r plus an atom. We also determine separately the ground state of the full 3 N-dimensional nuclear Schrodinger equation for the ground state, and compar e the resulting structural properties with those calculated in the adiabati c hyperspherical approximation. (C) 2000 American Institute of Physics. [S0 021-9606(00)31834-7].