On the Hylleraas functional for a non-Hermitian unperturbed Hamiltonian

摘要

The expression of the second-order Hylleraas functional is discussed for the case when the Hermitian Born-Oppenheimer Hamiltonian is decomposed into a non-Hermitian unperturbed part and a non-Hermitian perturbation. The result is of importance for developing BSSE-free perturbation theories of intermolecular interactions.