Atomic Multiconfiguration Self-Consistent-Field Wavefunctions

The ground‐state ${}^{1}S$ wavefunctions of the atomic isoelectronic series with two and four electrons ($\text{Z\hspace{0.17em}=\hspace{0.17em}1\hspace{0.17em}–\hspace{0.17em}8}$ , and 3–8, respectively), were calculated using the MC–SCF method restricted to pair replacements. These calculations were to test and demonstrate how rapidly the configuration expansions of the MC–SCF wavefunctions converge. In the two‐electron series, nine configurations were required to yield 97% of the correlation energy, while ten configurations accounted for 86% of the correlation energy in the four‐electron series. The quality of the reported wavefunctions has been tested by computing the expectation values of several one‐ and two‐electron operators. The results obtained agree in general satisfactorily (deviations of ∼1%) with values computed from more complex wavefunctions, indicating that the compact MC–SCF functions reported are indeed of high quality.