Multireference Equation of Motion Coupled Cluster study of atomic excitation spectra of first-row transition metal atoms Cr, Mn, Fe and Co

0443666 - ÚFCH JH 2016 RIV US eng J - Článek v odborném periodiku
Liu, Z. - Demel, Ondřej - Nooijen, M.
Multireference Equation of Motion Coupled Cluster study of atomic excitation spectra of first-row transition metal atoms Cr, Mn, Fe and Co.
Journal of Molecular Spectroscopy. Roč. 311, SI (2015), s. 54-63. ISSN 0022-2852. E-ISSN 1096-083X
Institucionální podpora: RVO:61388955
Klíčová slova: multireference * coupled cluster * electronic excited states
Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
Impakt faktor: 1.593, rok: 2015

Variants of the family of the recently developed Multireference Equation of Motion Coupled Cluster (MR-EOMCC) approaches are applied to the atomic excitation spectra of the neutral and the +1 and +2 charged first-row transition metal atoms Cr, Mn, Fe and Co. Scalar relativistic effects are considered but spin-orbit coupling is not included. Using a single set of state-averaged CASSCF orbitals and a single set of cluster amplitudes, a large number of excited states is obtained from the diagonalization of a compact transformed Hamiltonian. Hundreds of excited states (10's of L-S multiplets) are obtained for each atomic species with RMS errors compared to J-averaged experimental values that typically fall below 0.1. eV. All electronic states in MREOM are properly spin- and symmetry adapted. The cluster operators included in the variations of MREOM are denoted T, S, X, D and U. The inclusion of additional cluster operators is shown to yield a threefold benefit: (1) By inclusion of additional cluster amplitudes the size-extensivity error in MR-EOMCC is reduced. (2) The accuracy of the results is significantly increased as operators T, S, X and D are included. (3) The overall cost of the calculations is significantly reduced with increasing inclusion of cluster amplitudes as the dimension of the final diagonalization step can be greatly reduced. In the most compact MREOM-T|SXD|U-min approach the final diagonalization step is over a Hilbert space containing the active space CI determinants (CASCI), and 1-hole and 1-particle excitations out of the CAS.
Trvalý link: http://hdl.handle.net/11104/0246349