Simple accurate coupled cluster results for the linear E⊗e pseudo-Jahn-Teller effect

Abstract

Calculations for the energies of the ground and first excited states of the linear E⊗e Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) Hamiltonians are presented using the coupled cluster method (CCM). The PJT Hamiltonian considers the case of nonzero fermionic level splitting. These models contain interesting symmetries and are ideal testing grounds for approximate many-body methods. The calculations are presented in an operator-based form. The results are obtained with a maximal error of 1.2%.