Comparative analysis of nonrelativistic and relativistic calculations of electric dipole moments and polarizabilities of heteronuclear alkali-metal dimers

We analyze the molecular electric dipole moments (PDMs) and static electric dipole polarizabilities of heteronuclear alkali dimers in their ground states by employing coupled-cluster theory, both in the nonrelativistic and four-component relativistic frameworks. The roles of electron correlations as well as relativistic effects are demonstrated by studying them at different levels of theory, followed by a comprehensive treatment of error estimates. We compare our obtained values with the previous nonrelativistic calculations, some of which include lower-order relativistic corrections, as well as with the experimental values, wherever available. We find that the PDMs are sensitive to relativistic effects as compared to polarizabilities. We show that consideration of relativistic values of PDMs improves significantly the isotropic van der Waals C6 coefficients of the investigated alkali dimers over the previously reported nonrelativistic calculations. The dependence of dipole polarizabilites on molecular volume is also illustrated.