Quadrupole moments of CuH, AgH, and AuH. A study of the electron correlation and relativistic effects.

High-level correlated calculations of the quadrupole moment of the group-Ib hydrides have been carried out with large Gaussian-type-orbital/contracted-Gaussian-type-orbital basis sets. The nonrelativistic results obtained for CuH, AgH, and AuH at the self-consistent-field Hartree–Fock level of approximation and for the origin at the heavy atom are -2.16, -3.17, and -1.94 a.u., respectively. The electron correlation contribution computed by using the coupled-cluster approaches reduces those values to -0.25, -1.14, and -0.18 a.u., respectively. The relativistic corrections have been obtained from the recently developed quasirelativistic method. They have been found to be of increasing importance for the investigated series of hydrides. The final relativistically corrected values of molecular quadrupole moments are found to be small for CuH (+0.05 a.u.) and AgH (-0.36 a.u.) while the corresponding value for AuH is large and positive (+2.00 a.u.). [ABSTRACT FROM AUTHOR]