title: Analytical energy gradient used in variational Born-Oppenheimer calculations with all-electron explicitly correlated Gaussian functions for molecules containing one π electron.
abstract: An algorithm for variational calculations of molecules with one π electron performed with all-electron explicitly correlated gaussian (ECG) functions with floating centers is derived and implemented. The algorithm includes the analytic gradient of the Born-Oppenheimer electronic energy determined with respect to the ECG exponential parameters and the coordinates of the gaussian centers. The availability of the gradient greatly accelerates the variational energy minimization. The algorithm is tested in calculations of four electronic excited states, c(3)Π(u), C(1)Π(u), i(3)Π(g), and I(1)Π(g), of the hydrogen molecule at a single internuclear distance specific to each state. With the use of the analytical energy gradient, the present calculations yield new, lowest-to-date, variational energy upper bounds for all four states.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Tung
authors.forename: Michele
authors.initials: M
authors.lastname: Pavanello
authors.forename: Keeper L
authors.initials: KL
authors.lastname: Sharkey
authors.forename: Nikita
authors.initials: N
authors.lastname: Kirnosov
authors.forename: Ludwik
authors.initials: L
authors.lastname: Adamowicz
mesh_terms: D000465:Algorithms; D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D011789:Quantum Theory
chemical_list: D006859:Hydrogen