WAVE-FUNCTION OPTIMIZATION BY LEAST-SQUARES FITTING OF THE EXACT WAVE-FUNCTION SAMPLED BY QUANTUM MONTE-CARLO

The sampling of the exact solution of the Schrodinger equation by quan tum Monte Carlo methods allows one to solve the problem of the optimiz ation of linear and nonlinear parameters of a trial wave function by m inimization of the distance to the exact wave function in Hilbert spac e even for those systems whose exact wave function is unknown The over lap integrals between the basis functions and the exact wave function can be easily estimated within the quantum Monte Carlo formalism. Seve ral observables of the helium atom ground state, computed both within the orbital approximation and by an explicitly correlated basis set, e vidence the overall goodness of the wave function optimized according to this criterion. (C) 1996 John Wiley & Sons, Inc.