On the (N, Z) dependence of the second-order Møller-Plesset correlation energies for closed-shell atomic systems

Accurate Moller-Plesset (MP2) correlation energies calculated by means of the variational-perturbation and the finite-element methods are presented for several members of the Cu+ isoelectronic series (N = 28), which represent closed-shell systems containing for the first time the 3d10-electron configuration and, consequently, closed M-shell. Total MP2 energies as well as their inner- and inter-shell components are reported for Cu+, Zn2+, Ge4+, Kr8+, Sr10+, and Cd20+. We found that for these ions the Z-dependence of the total MP2 energies is significantly weaker than for the members of the Ar-like series. The origin of this fact is rationalized by a detailed analysis performed at the levels of the shell- and inter-shell contributions to the MP2 energies. To get, for the first time, more general information about the (N, Z) characteristics of the MP2 energies for closed-shell atomic systems, we compare the Z-dependence of the Cu+-like systems with the MP2 energies calculated for other isoelectronic series. ...