title: Calculation of current densities using gauge-including atomic orbitals.
abstract: A method for calculating the various components of the magnetically induced current-density tensor using gauge-including atomic orbitals is described. The method is formulated in the framework of analytical derivative theory, thus enabling implementation at the Hartree-Fock self-consistent-field (HF-SCF) as well as at electron-correlated levels. First-order induced current densities have been computed up to the coupled-cluster singles and doubles level (CCSD) augmented by a perturbative treatment of triple excitations [CCSD(T)] for carbon dioxide and benzene and up to the full coupled-cluster singles, doubles, and triples (CCSDT) level in the case of ozone. The applicability of the gauge including magnetically induced current method to larger molecules is demonstrated by computing first-order current densities for porphin and hexabenzocoronene at the HF-SCF and density-functional theory level. Furthermore, a scheme for obtaining quantitative values for the induced currents in a molecule via numerical integration over the current flow is presented. For benzene, a perpendicular magnetic field induces a (field dependent) ring current of 12.8 nA T(-1) at the HF-SCF level using a triple-zeta basis set augmented with polarization functions (TZP). At the CCSD(T)/TZP level the induced current was found to be 11.4 nA T(-1). Gauge invariance and its relation to charge-current conservation is discussed.
authors.affiliation: Department of Chemistry, P.O. Box 55 (A.I. Virtasen Aukio 1), FIN-00014 University of Helsinki, Helsinki, Finland. jonas@chem.helsinki.fi
authors.forename: Jonas
authors.initials: J
authors.lastname: Jusélius
authors.forename: Dage
authors.initials: D
authors.lastname: Sundholm
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gauss