Correlation Energy of Twohyphen;Electron Systems

摘要

Correlated closedhyphen;shell and openhyphen;shell functions (due to Roothaan and Weiss) are analyzed in terms of a 1/Zexpansion to obtain the corresponding firsthyphen;order wavefunctions and the secondhyphen;order energy. The need for expanding the openhyphen;shell functions in powers ofZmdash;frac12;is demonstrated. The contributions to the secondhyphen;order energy from radial and angular correlation are estimated.