title: Relativistic internally contracted multireference electron correlation methods.
abstract: We report internally contracted relativistic multireference configuration interaction (ic-MRCI), complete active space second-order perturbation (CASPT2), and strongly contracted n-electron valence state perturbation theory (NEVPT2) on the basis of the four-component Dirac Hamiltonian, enabling accurate simulations of relativistic, quasi-degenerate electronic structure of molecules containing transition-metal and heavy elements. Our derivation and implementation of ic-MRCI and CASPT2 are based on an automatic code generator that translates second-quantized ansätze to tensor-based equations, and to efficient computer code. NEVPT2 is derived and implemented manually. The rovibrational transition energies and absorption spectra of HI and TlH are presented to demonstrate the accuracy of these methods.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Rd., Evanston, Illinois 60208, United States.
authors.forename: Toru
authors.initials: T
authors.lastname: Shiozaki
authors.affiliation: Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University , 6-1 Kasuga-Park, Fukuoka, 816-8580, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Mizukami