Range of Electron Correlation in the Helium Atom

摘要

For the helium atom, a new type of correlation factor is tested which has the form 1+ch(r12) whereh(r12) is a cutoff correlation variable such thath(r12) =r12for 0le;r12le;D,andh(r12) =DforDle;r12le;infin;, withcandDadjustable parameters. In a series of energy calculations using wavefunctions which contain both configuration interaction and cutoffr12terms, it is found that, as far as the energy is concerned: (1) The correlation cusp is unimportant, and (2) The range of the Coulomb correlation effect is of the order of the atomic diameter. For very smallD,the correlation energy per unit volume is calculated to be 0.048 hartree/bohr3.