INTERATOMIC FORCES AND CORRELATED SAMPLING IN QUANTUM MONTE CARLO

One of the main difficulties of quantum Monte Carlo techniques is the lack of an efficient method for computing interatomic forces. To date, most quantum Monte Carlo calculations have been performed on geometries obtained with either density functional theory or conventional quantum chemistry methods. Here, we present a correlated sampling method to efficiently calculate numerical forces and potential energy surfaces in diffusion Monte Carlo. It employs a novel coordinate transformation, earlier used in variational Monte Carlo, to greatly reduce the statistical error. Results are presented from all-electron and pseudopotential calculations of homonuclear diatomic molecules.