title: Direct Atomic-Orbital-Based Relativistic Two-Component Linear Response Method for Calculating Excited-State Fine Structures.
abstract: In this work, we present a linear-response formalism of the complex two-component Hartree-Fock Hamiltonian that includes relativistic effects within the Douglas-Kroll-Hess and the Exact-Two-Component frameworks. The method includes both scalar and spin relativistic effects in the variational description of electronic ground and excited states, although it neglects the picture-change and explicit spin-orbit contributions arising from the two-electron interaction. An efficient direct formalism of solving the complex two-component response function is also presented in this work. The presence of spin-orbit couplings in the Hamiltonian and the two-component nature of the wave function and Fock operator allows the computation of excited-state zero-field splittings of systems for which relativistic effects are dominated by the one-electron term. Calculated results are compared to experimental reference values to assess the quality of the underlying approximations. The results show that the relativistic two-component linear response methods are able to capture the excited-state zero-field splittings with good agreement with experiments for the systems considered here, with all approximations exhibiting a similar performance. However, the error increases for heavy elements and for states of high orbital angular momentum, suggesting the importance of the two-electron relativistic effect in such situations.
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Franco
authors.initials: F
authors.lastname: Egidi
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Goings
authors.affiliation: Gaussian, Inc., 340 Quinnipiac St., Bldg. 40, Wallingford, Connecticut 06492, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Frisch
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Li