Quasirelativistic multipartitioning perturbation theory calculations on electronic transitions in Au2

UV–visible absorption of small gold clusters in neon: Aun (n = 1–5 and 7–9)

“…However, neither results are in good agreement with the gas phase or matrix absorption spectra, in particular the two intense A and B transitions are not reproduced. It is worth to notice that more elaborate calculations [56][57][58] which take explicitly into account the spin-orbit coupling are in much better agreement with the dimer gas phase experimental absorption spectra. This is a clear indication that the lack of spin-orbit splitting in the TD-DFT calculations results in a serious limitation to reproduce the experimental spectra.…”

“…The gold dimer has been calculated, including the excited states, using Hartree-Fock and DFT methods. [56][57][58][59] Similar techniques were applied to determine the ground state geometries of the trimer, 60-63 the tetramer, 60,62,64 and the pentamer. 62,64 DFT calculations have been performed more recently in order to predict the lowest energy structures 12-14, 16, 18, 19, 31 and to calculate the optical spectra by TFD-DFT for clusters up to Au 14 and Au 20 .…”

On excited states of the Au3 cluster: an ab initio study

“…A state-selective effective Hamiltonian is built in a model space spanned by Slater determinants following the procedure reported in Ref. [12]. The spin-orbit interactions between the model and outer spaces are completely neglected.…”

“…The spin-orbit interactions between the model and outer spaces are completely neglected. Therefore, additional requirements on the model space and a procedure for its composition are imposed [12]. The procedure employed is based on the spin-orbit-free iterative perturbative configuration selection against a threshold [13].…”

“…To improve the description of spin-orbit effects associated with the onebody spin-orbit pseudopotential operator, a lower selection threshold is set for configurations evolving from single excitations of the leading determinants. The details of the procedure are reported elsewhere [1,12]. Since the energies and wavefunctions of the ground state with a filled 5 shell and excited states with 5 holes are calculated simultaneously, it is highly desirable that the common set of molecular orbitals be well-balanced for 5 9 -and 5 10 -like occupancies.…”