Size-consistent self-consistent truncated or selected configuration interaction

摘要: Based on the principle of intermediate effective Hamiltonians, a simple procedure is proposed in order to eliminate unlinked contributions any truncated or selected configuration interaction (CI). The corrections are diagonal energy shifts, easily calculated. A self‐consistent version proposed, which insures separability if localized molecular orbitals (MO) used. In special case double CI, present method an improved coupled electron pair approximation (CEPA), but it may be applied model space, involving configurations various degrees excitation. efficiency algorithms illustrated series test calculations performed Be2, F2, N2, and NH3.