Compact 1 1S helium wave functions

A highly compact four-parameter form for helium's approximate nonrelativistic wave function is proposed and shown to yield an energy expectation value within 0.003 a.u. of the 'exact' value. The wave function employs proper atomic-number-parametrized hydrogenic orbitals and a correlation function whose form is [1+(1/2)r12e-αr12], coupled with a variationally determined expansion in r1, r2, and r12