Accurate, efficient, and simple forces computed with quantum Monte Carlo methods

Phys Rev Lett. 2005 Jan 28;94(3):036404. doi: 10.1103/PhysRevLett.94.036404. Epub 2005 Jan 24.

Abstract

Computation of ionic forces using quantum Monte Carlo methods has long been a challenge. We introduce a simple procedure, based on known properties of physical electronic densities, to make the variance of the Hellmann-Feynman estimator finite. We obtain very accurate geometries for the molecules H(2), LiH, CH(4), NH(3), H(2)O, and HF, with a Slater-Jastrow trial wave function. Harmonic frequencies for diatomics are also in good agreement with experiment. An antithetical sampling method is also discussed for additional reduction of the variance.