Solvent configuration-interaction calculations of intermolecular states in molecule-(atom)N clusters: Application to Br2–4HeN.

We describe variational calculations of J=0 intermolecular states in Br2–4HeN clusters. The method employed is analogous to configuration-interaction calculations in electronic-structure work and relies on the ability to express the intermolecular Hamiltonian H⁁v as a sum of one- and two-body terms. A basis set is built up from solutions to the Schrödinger equation in which only the one-body terms of H⁁v are included. These configurations are products of N=1 eigenstates. The matrix of H⁁v in a symmetry-adapted configuration basis is then computed, the two-body terms of H⁁v serving to couple different configurations. This computation involves integrals of dimension five or less. Filter diagonalization is then used to obtain energies and eigenfunctions within a selected energy range. Results on clusters having N=2–5 are reported. [ABSTRACT FROM AUTHOR]