A theoretical study of BeN linear chains: Variational and perturbativeapproaches

摘要

A systematic theoretical study of BeN linear chains by means of both variational (multireferenceconfiguration interaction) and perturbative (n-electron valence state perturbation theory)methodologies is reported. Extensive calculations have been performed using atomic natural orbitalbasis set of increasing size (3slp, 4s2pld, and 5s3p2dlf). The problematic task of obtaining acoherent description of the potential energy surface with approximate ab initio methods isaddressed. The main difficulty met in the computation of the binding energy of long BeN chainsessentially arises from the need of using, as the dissociation is approached, a variational spacedifferent from that suitable to treat the system near the equilibrium distance. To overcome thisproblem, two alternative approaches are presented and the computed dissociation energies arecompared to the corresponding full-CI values reported in a recent work [V. Vetere et al., J. Chem.Phys. 130, 024301 (2009)].