title: Spin-adaptation and redundancy in state-specific multireference perturbation theory.
abstract: Spin-adaptation of virtual functions in state-specific multireference perturbation theory is examined. Redundancy occurring among virtual functions generated by unitary group based excitation operators on a model-space function is handled by canonical orthogonalization. The treatment is found to remove non-physical kinks observed earlier on potential energy surfaces. Sensitivity analysis of the new approach confirms the elimination of the drastic increase in singular values of sensitivity matrices, reported earlier.
authors.affiliation: Laboratory of Theoretical Chemistry, Loránd Eötvös University, H-1518 Budapest, POB 32, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Jeszenszki
authors.forename: Péter R
authors.initials: PR
authors.lastname: Surján
authors.forename: Ágnes
authors.initials: Á
authors.lastname: Szabados
mesh_terms: D001128:Argon / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D004058:Diffusion; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002245:Carbon Dioxide; D001128:Argon