Application of MP2 results in comparative studies of semiempirical ground-state energies of large atoms

To study the usefulness of second-order Moller-Plesset (MP2) correlation energies for ground states of closed-shell atoms (referred to as MP2/CA energies) in estimations of the total correlation energies of larger closed-shell atoms, we have considered atoms and ions containing from 10 to 86 electrons. First, it is demonstrated that for N-electron systems, 10 less than or equal to N less than or equal to 18, the MP2/CA energies provide very good approximations to the very accurate estimates of atomic correlation energies by Chakravorty and Davidson. Next, for systems with 10 less than or equal to N less than or equal to 54, comparisons are made with the semiempirical energies obtained when using the models by Chakravorty and Clementi as well as by Clementi and Corongiu. Finally, for atoms with 10 less than or equal to N less than or equal to 86, the MP2/CA energies are employed for comparison with DFT energies recently obtained by Andrae et al. (Int. J. Quantum Chem. 2001, 82, 227). The MP2/CA results proved to provide reasonable estimates to the total correlation energies in all the cases considered.