Choosing RASSCF orbital active spaces for multiple electronic states

Florian Krausbeck (1) , David Mendive-Tapia (2) , Alex J. W. Thom , Michael J. Bearpark (3)

1 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
2 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
3 Department of Chemistry [Imperial College London]

A systematic approach is introduced for defining Restricted Active Space Self-Consistent-Field (RASSCF) orbitals for treating multiple electronic states in a balanced way, based on an SCF state-averaging procedure (Thom and Head-Gordon, 2008). We start from an SCF density matrix averaged over the electronic states of interest and choose a RAS partition based on the corresponding natural orbital occupation numbers. In order to test this procedure, we apply it to naphthalene cation, previously studied as a potential interstellar Polycyclic Aromatic Hydrocarbon (PAH) because of its photo stability following electronic excitation (Hall et al., 2006). The results obtained with this method in terms of energies and bond lengths for the first three electronic states and the corresponding minimum energy conical intersections between potential energy surfaces compare very well with CASSCF results and suggest further testing of the method for RASSCF calculations. (C) 2014 Elsevier B.V. All rights reserved.

Domaines: Chimie

Florian Krausbeck, David Mendive-Tapia, Alex J. W. Thom, Michael J. Bearpark. Choosing RASSCF orbital active spaces for multiple electronic states. Computational and Theoretical Chemistry, 2014, 1040 (SI), pp.14-19. ⟨10.1016/j.comptc.2014.03.030⟩. ⟨hal-02142258⟩