On the choice of active space orbitals in MCSCF calculations |
| |
Authors: | David M Rogers Claire Wells Melanie Joseph Vanessa J Boddington Joseph JW McDouall |
| |
Affiliation: | a Department of Chemistry, University of Manchester Manchester M13 9PL UK |
| |
Abstract: | We describe a procedure which may be used to aid selection of the active space in multiconfigurational self-consistent field (MCSCF) calculations for general chemical systems. Starting from a restricted Hartree-Fock calculation, we define a hierarchy of interacting virtual orbitals for every occupied orbital. The most strongly interacting orbitals are then taken to constitute the active space in a configuration interaction (CI) calculation. The natural orbital occupation numbers obtained from the CI calculation are then used to choose the active space to be used in a subsequent MCSCF calculation. We illustrate our method on a number of systems (Li2, B2, C2, carbonyl oxide and the transition state for oxidation of H2S by dioxirane). In all these cases, ‘intuitive’ active spaces are inadequate, as are active spaces derived from the natural orbitals of unrestricted Hartree-Fock calculations. |
| |
Keywords: | MCSCF Choice of active space Orbital interactions |
本文献已被 ScienceDirect 等数据库收录! |