Ab initiocalculation of theXthinsp;1Sgr;+state of CsH

摘要

Relativistic effective core potential (RECP) and nonrelativistic all electron (NRAE) calculations are reported for theXthinsp;1Sgr;+state of CsH. The calculations are based on GVB plus single and double excitation CI wave functions with the Cs(5s, 5p) as well as the two valence electrons correlated. The bonding in CsH is found to involve a Cs(6s)ndash;H(1s) bond but with a significant ionic (Cs+Hminus;) component. Correlating the Cs(5s, 5p) electrons leads to a significant bond shortening effect (sim;0.15a0). This effect is attributed to a contraction of the Cs(6s) orbital and a shift toward higher energy of the Cs+Hminus;asymptote upon correlating the 5s, 5pshell. Bond shortening due to relativistic contraction of the Cs(6s) is only sim;0.05a0in agreement with the small amount of Cs(6s) character in the ionic bond orbital. The NRAE and RECP potential curves are very similar except for the shorterRefor the RECP case (due to relativistic bond contraction).