Inclusion of correlations in He, Be, and Ne by the configuration interaction method

The influence of various approximations used to include correlations in He, Be, and Ne atoms on correlation energies and on the structure of correlation functions is analyzed. The effects of three-and four-electron correlations are evaluated. For He, Be, and Ne atoms, the correlation energies were found to equal 99.99, 100.11, and 97.9% of the experimental value, respectively. A method of obtaining a one-electron function basis is proposed to ensure the best convergence of correlation energies as the number of included configurations increases. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1001–1012, November–December, 1998.