Resonance study: Effect of partial triples excitation using complex absorbing potential‐based Fock‐space multi‐reference coupled cluster.

Resonances are metastable states with finite lifetime. They play important role in physics, chemistry and biology. The theoretical calculation of resonance state is a challenging problem. In this paper we have studied the shape resonance of Be, Mg, N2 and CO. We have used correlated independent particle approximation to the Fock space multi‐reference coupled cluster singles‐doubles with third‐order triples (CAP‐CIP‐FSMRCCSD(T)) method augmented by complex absorption potential. The resonance energy and decay widths are obtained by solving a non‐Hermitian eigen‐value problem within FSMRCC framework. The effects of the lowest order triples on the resonance energy and decay are studied. [ABSTRACT FROM AUTHOR]