title: Analytical gradients of the state-average complete active space self-consistent field method with density fitting.
abstract: An efficient implementation of the state-averaged complete active space self-consistent field (SA-CASSCF) gradients employing density fitting (DF) is presented. The DF allows a reduction both in scaling and prefactors of the different steps involved. The performance of the algorithm is demonstrated on a set of molecules ranging up to an iron-Heme b complex which with its 79 atoms and 811 basis functions is to our knowledge the largest SA-CASSCF gradient computed. For smaller systems where the conventional code could still be used as a reference, both the linear response calculation and the gradient formation showed a clear timing reduction and the overall cost of a geometry optimization is typically reduced by more than one order of magnitude while the accuracy loss is negligible.
authors.affiliation: Department of Chemistry - Ångström, The Theoretical Chemistry Programme, Uppsala University, P.O. Box 518, 751 20 Uppsala, Sweden.
authors.forename: Mickaël G
authors.initials: MG
authors.lastname: Delcey
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, Norway.
authors.forename: Thomas Bondo
authors.initials: TB
authors.lastname: Pedersen
authors.affiliation: Department of Chemistry - Ångström, The Theoretical Chemistry Programme, Uppsala University, P.O. Box 518, 751 20 Uppsala, Sweden.
authors.forename: Francesco
authors.initials: F
authors.lastname: Aquilante
authors.affiliation: Department of Chemistry - Ångström, The Theoretical Chemistry Programme, Uppsala University, P.O. Box 518, 751 20 Uppsala, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh