Accurate electric field gradients for the coinage metal chlorides using the PCNQM method

Accurate nonrelativistic and Douglas–Kroll coupled-cluster calculations for the electric field gradients (EFG) of the coinage metal chlorides are presented using the point-charge model for the nuclear quadrupole moment (PCNQM). It is shown that especially for gold chloride the picture-change error does not allow for an accurate determination of the EFG by the expectation value over the EFG tensor. For AuCl relativistic effects lead to the interesting case where both the Au and Cl EFG are positive. Relativistic effects in the Cl EFGs are large especially in AuCl, which is mainly due to the relativistic change in the valence electron density.