title: Communication: Analytic gradients in the random-phase approximation.
abstract: The relationship between the random-phase-approximation (RPA) correlation energy and the continuous algebraic Riccati equation is examined and the importance of a stabilizing solution is emphasized. The criterion to distinguish this from non-stabilizing solutions can be used to ensure that physical, smooth potential energy surfaces are obtained. An implementation of analytic RPA molecular gradients is presented using the Lagrangian technique. Illustrative calculations indicate that RPA with Hartree-Fock reference orbitals delivers an accuracy similar to that of second-order Mo̸ller-Plesset perturbation theory.
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
authors.forename: Johannes
authors.initials: J
authors.lastname: Rekkedal
authors.forename: Sonia
authors.initials: S
authors.lastname: Coriani
authors.forename: Maria Francesca
authors.initials: MF
authors.lastname: Iozzi
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Teale
authors.forename: Trygve
authors.initials: T
authors.lastname: Helgaker
authors.forename: Thomas Bondo
authors.initials: TB
authors.lastname: Pedersen