Relativistic four-component static-exchange approximation for core-excitation processes in molecules

Ekström, UlfLinköpings universitet,Beräkningsfysik,Tekniska högskolan (författare)

QC 20190119
A generalization of the static-exchange approximation for core-electron spectroscopies to the relativistic four-component realm is presented. The initial state is a Kramers restricted Hartree-Fock state and the final state is formed as the configuration-interaction single excited state, based on the average of configurations for (n-1) electrons in n near-degenerate core orbitals for the reference ionic state. It is demonstrated that the static-exchange Hamiltonian can be made real by considering a set of time-reversal symmetric electron excitation operators. The static-exchange Hamiltonian is constructed at a cost that parallels a single Fock matrix construction in a quaternion framework that fully exploits time-reversal and spatial symmetries for the D2h point group and subgroups. The K - and L -edge absorption spectra of H2 S are used to illustrate the methodology. The calculations adopt the Dirac-Coulomb Hamiltonian, but the theory is open ended toward improvements in the electron-electron interaction operator. It is demonstrated that relativistic effects are substantial for the L -edge spectrum of sulfur, and substantial deviations from the statistical 2:1 spin-orbit splitting of the intensity distribution are found. The average ratio in the mixed region is 1.54 at the present level of theory.

Norman, PatrickLinköpings universitet,Beräkningsfysik,Tekniska högskolan(Swepub:liu)patno81 (författare)
Carravetta, V.Istituto per i Processi Chimico-Fisici, Area della Ricerca del C.N.R., Pisa, Italy (författare)
Linköpings universitetBeräkningsfysik (creator_code:org_t)

Ingår i:Physical Review A. Atomic, Molecular, and Optical Physics: American Physical Society73:21050-29471094-1622

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