Nuclear electric quadrupole moment of gold from the molecular method

The nuclear electric quadrupole moment (NQM) of gold is reviewed by means of the molecular method and data from as many as 15 linear systems. The electric-field gradients (EFGs) used to this end were obtained with the Dirac-Coulomb Hamiltonian and coupled-cluster theory, CCSD(T) and CCSD-T, by means of an augmented relativistic basis set for gold. The direct approach was found to be inadequate for the diatomic molecules investigated, which is probably due to improper treatment of the static electron correlation. However, these effects are much less relevant for OCAuX (X = F, Cl, Br, and I) complexes. Thus, the indirect version of the molecular method is preferred in this case. Hence, a NQM value of 515(15) mb is determined for Au-197 from linear regressions performed with the best EFGs determined for ten of these systems.