Comparative study of electron correlation and relativistic effects in CuF, AgF, and AuF

Spectroscopic and electric properties of the series of diatomic molecules FCu, FAg, and FAu are calculated using the coupled cluster CCSD(T) method and considering relativistic effects by the no-pair one-component Douglas-Kroll-Hess approximation. The correlation and relativistic effects in the FM series (M = Cu, Ag, Au) are compared with these effects in the AlM series. Differences in the bonding character and consequently also in molecular properties in FM and AIM are primarily due to different relativistic effects in both series. Relativity destabilized all bonds in the FM series but led to the increase of bond energy in all AlM diatomics. At the same time correlation effects were similar in all FM and AlM molecules, making all bonds considerably stronger. The different influences of relativistic effects on the bond energy are interpreted in traditional terms of electronegativities of constituent atoms supplemented by the comparative analysis of correlation and relativistic effects on electric properties in both the FM and the AlM series. The polarity of FM and AlM molecules is opposite and the dipole polarizabilities in the FM series are much lower than those in the AlM series.