Molecular Schrödinger Equation. III. Calculation of Ground-State Energies by Extrapolation

The problem of optimization of the parameters in a trial wavefunction can be approached through the minimization of the energy variance function, a procedure which offers certain important advantages over the customary one where the energy function itself is minimized. The use of an energy variance calculation further permits extrapolation to a more accurate approximation to the true energy than can be attained solely from a knowledge of the ordinary upper and lower bounds. Specific computational procedures are discussed.