Application of MP2 Results in Comparative Studies of Semiempirical Ground-State Energies of Large Atoms

To study the usefulness of second-order Møller-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 ≤ N ≤ 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 ≤ N ≤ 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 ≤ N ≤ 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.