Electronic Wave Functions for Atoms. IV. Ground State of Ne

The configuration-interaction (CI) method is employed in an exhaustive investigation of the ground state of Ne. A 231-term CI expansion (formed from a determinantal space of dimension 5343), obtained with an optimized $6s6p5d4f$ basis, gives an energy $E=-128.\mathrm{}8868$ a.u. (Ne). The Ne wave function is compared with those of ${\mathrm{Ne}}^{6+}$ and ${\mathrm{Ne}}^{8+}$. A quantitative assessment of all sources of truncation errors is given. The nonrelativistic energy is estimated to be -128.932±0.008 a.u. (Ne), in agreement with previous estimates obtained by different methods. Three- and four-excited determinants are shown to contribute 1% of the correlation energy. The $L$-shell correlations are shown to be nonadditive. Also, about 8% of the correlation energy is given by configurations containing $g$, $h$, and higher harmonics.