Electron correlation trends in the permanent electric dipole moments of alkaline-earth-metal monohydrides

Abstract

We report the results of our theoretical studies of the permanent electric dipole moments (PDMs) of alkaline-earth-metal monohydride (AEMH) molecules, in their $X{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}^{+}$ state, using a variant of the relativistic coupled-cluster theory in the singles and doubles approximation. It is the most detailed evaluation to date of the correlation effects associated with this property for this class of molecules. The molecules that have been considered in the present work are BeH, MgH, CaH, SrH, and BaH. We find that for SrH and BaH, the correlation contributions to the PDM are significant, about 18% and 21%, respectively, at the coupled-cluster singles and doubles level. All the core electrons have been excited in our calculations. We highlight the details of the individual contributions of different classes of correlation effects. For all the above molecular candidates, we have also made a comprehensive analysis of the possible sources of error in our calculations.