Reliable diffusion quantum Monte Carlo

Abstract

By introducing perturbations of O(τ) type (where τ is the time step used in the simulation) to our diffusion quantum Monte Carlo algorithm we obtain a simulated energy which is reasonably constant over a wide range of τ values. Reliable estimation of the fixed-node energy (τ=0 intercept) results, as extrapolation becomes more robust and a radical change in small τ behavior becomes less likely. We apply our techniques to the problem of estimating the ground-state energy of LiH and H2O.