State specific calculation of dissociation potential energy curve using multireference perturbation theory

Abstract

We have applied multireference (MR) perturbation theory to a degenerate case using the state-specific or single root MR approach (SS-MRPT). The objective of this paper is to provide an account of the applications of both Brillouin-Wigner and Rayleigh-Schrodinger versions of the SS-MRPT with Moller-Plesset partitioning of the hamiltonian. The method is very effective to provide an accurate and balanced treatment of dynamical and non-dynamical correlations over a wide range of geometrical parameters of the molecule under study, and hence, seeks to address bond breaking process in an accurate manner. Studies on dissociation potential energy curve and spectroscopic constants of the ground state of F2 are carried out to gauge its accuracy. F2 is a particularly challenging system for electronic structure theory due to strong dynamical and non-dynamical correlation effects. The calculations are compared with other available theoretical results and experimental spectroscopic data. The accuracy of the results appears to be encouraging, taking into account the low computational cost which supports the effectiveness of the method.