RAPIDLY CONVERGING HIGH-PRECISION HE GROUND-STATE ENERGIES THROUGH THE USE OF SYSTEMATICALLY CONSTRUCTED GAUSSIAN GEMINALS

Systematically constructed r12-dependent Gaussian geminals which contain the factor exp(-gammar12(2) enable rapid convergence of the non-relativistic electronic energy for the helium atom, leaving an error of 10(-6) au for a CI dimension of N = 275, 3 x 10(-8) au for N = 636, and only 3 X 10(-10) au for N = 1648, i.e. each time the dimension N is increased by a factor of 1.7, an additional correct decimal digit is obtained. The best helium energy calculated in this study, represents an improvement by more than three orders of magnitude over previous Gaussian geminal results.