title: Vibrational contributions to indirect spin-spin coupling constants calculated via variational anharmonic approaches.
abstract: Zero-point vibrational contributions to indirect spin-spin coupling constants for N2, CO, HF, H2O, C2H2, and CH4 are calculated via explicitly anharmonic approaches. Thermal averages of indirect spin-spin coupling constants are calculated for the same set of molecules and for C2X4, X = H, F, Cl. Potential energy surfaces have been calculated on a grid of points and analytic representations have been obtained by a linear least-squares fit in a direct product polynomial basis. Property surfaces have been represented by a fourth-order Taylor expansion around the equilibrium geometry. The electronic structure calculations employ density functional theory, and vibrational contributions to indirect spin-spin coupling constants are calculated employing vibrational self-consistent-field and vibrational configuration-interaction methods. The performance of vibrational perturbation theory and various approximate variational calculations are discussed. Thermal averages are computed by state-specific and virtual vibrational self-consistent-field methods.
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Department of Chemistry, University of Arhus, Langelandsgade 140, DK-8000 Arhus C, Denmark. mbh@chem.au.dk
authors.forename: Mikkel B
authors.initials: MB
authors.lastname: Hansen
authors.forename: Jacob
authors.initials: J
authors.lastname: Kongsted
authors.forename: Daniele
authors.initials: D
authors.lastname: Toffoli
authors.forename: Ove
authors.initials: O
authors.lastname: Christiansen