AuSi molecule revisited: IOTC/CASSCF/CASPT2 calculations

Abstract

The results of theoretical calculations for the ground and low‐lying excited states of the AuSi molecule are presented. Calculations were carried out using the spin‐free relativistic infinite‐order two‐component (IOTC) Hamiltonian in conjunction with the multistate CASPT2 method. For comparison, the ground state was also calculated using the IOTC‐CCSD(T) method. The spin‐orbit coupling is introduced via the restricted active space state interaction method with the use of the atomic mean‐field SO integrals. The results are compared with the available experimental and theoretical results. The spectroscopic parameters derived from the potential energy curves are presented. The results obtained suggest that the experimental data should be reconsidered.

Excited states of aurocarbons: CASPT2 and CCSD(T) calculations of C2Au2 and C2Au4

“…Numerous theoretical investigations on valence, Rydberg and valence/Rydberg mixed excited states of ethylene, including [26–70] offer deep insight into the understanding of (not easy) basic features of experimental electronic spectra of ethylene. In Table 6, we present results of our CASPT2 calculations in comparison with selected theoretical and experimental data from literature.…”

“…Upon extending the number of active orbitals in the active space with the same number of active electrons (6, 8, or 10 electrons, respectively) EEs with IPEA = 0.00 spread less than with IPEA = 0.25 for almost all states and both multiplicities (we can say that results are more stable and converge faster with IPEA = 0.00). Some other authors [65,66] also recommend rather omitting the denominator shift in similar situations. They also have demonstrated the dependence of the accuracy on the number of electrons in the system.…”