Ground state properties of cesium dimers from a b i n i t i o pseudopotential approaches

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Abstract
We present the results of several calculations of the ground state of Cs2 and Cs+2 performed in the local‐spin‐density approximation of density functional theory, and using different approximations for the core electrons in the derivation of ab initio norm‐conserving pseudopotentials. We investigate the influence of both core polarization and relativistic effects on the molecular bonding, which turns out to be of minor importance for the determination of the equilibrium characteristics. We find that in order to guarantee an accurate description within the one‐electron scheme, one must avoid the usual ‘‘linear’’ approximation of the exchange‐correlation functional in the derivation of the pseudopotentials. This introduces significant errors for Cs and most probably for all one‐electron systems.