title: Selected excitation for CAS-SDCI calculations.
abstract: A new selected-configuration interaction method is proposed, based on the use of local orbitals. A corresponding code has been written, which is devoted to CI calculations of rather large systems (about 50-100 carbon-like atoms). Taking advantage of the locality, and then of the fact that interactions vanish when the distance is large, the dimension of the CI space is largely reduced. The determinants that would be created by long range excitations are expected to have a small weight in the wave function and are therefore eliminated. This selected excitation CI space is particularly suited for large molecules. It is tested on large polyene chains and on a transition metal complex. For large enough systems, the CPU time saving is important and, what is more noticeable, calculations that were impossible to perform without selection are feasible in this approach.
authors.affiliation: Laboratoire de Chimie et Physique Quantiques, IRSAMC, Université Paul Sabatier, 118, Route de Narbonne, Toulouse Cedex 31062, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Bories
authors.forename: Daniel
authors.initials: D
authors.lastname: Maynau
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Bonnet
mesh_terms: D011090:Polyenes; D011789:Quantum Theory; D028561:Transition Elements
chemical_list: D011090:Polyenes; D028561:Transition Elements