Wave functions with terms linear in the interelectronic coordinates to take care of the correlation cusp. II. Second‐order Mo/ller–Plesset (MP2‐R12) calculations on closed‐shell atoms

The MP2‐R12 method in approximations A and B as outlined in part I of this series is applied to the ground states of the closed‐shell atoms He, Be, Ne, Mg, Ar, Ca, Cu⁺, Zn²⁺, and Kr, in terms of both STO and GTO basis sets. For He, Be, and Ne the partial wave increments of the various pairs are documented and compared with their conventional counterparts. The fast convergence of the partial wave increments, that go as (l+ (1)/(2) )⁻⁸ in the MP2‐R12/B scheme, is demonstrated. From the MP2‐R12 calculations more accurate estimates of the exact MP2 energies are possible than from the conventional partial wave expansion. The actually calculated values differ generally by a fraction of a 1% from the estimated basis sets limits if STO basis sets with l≤5 (in some cases l≤6) are used, while errors of typically 1% are obtained with GTO basis sets and l≤3.