title: Size-consistent variational approaches to nonlocal pseudopotentials: Standard and lattice regularized diffusion Monte Carlo methods revisited.
abstract: We propose improved versions of the standard diffusion Monte Carlo (DMC) and the lattice regularized diffusion Monte Carlo (LRDMC) algorithms. For the DMC method, we refine a scheme recently devised to treat nonlocal pseudopotential in a variational way. We show that such scheme-when applied to large enough systems-maintains its effectiveness only at correspondingly small enough time-steps, and we present two simple upgrades of the method which guarantee the variational property in a size-consistent manner. For the LRDMC method, which is size-consistent and variational by construction, we enhance the computational efficiency by introducing: (i) an improved definition of the effective lattice Hamiltonian which remains size-consistent and entails a small lattice-space error with a known leading term and (ii) a new randomization method for the positions of the lattice knots which requires a single lattice-space.
authors.affiliation: Centre de Physique Theorique, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France. casula@cpht.polytechnique.fr
authors.forename: Michele
authors.initials: M
authors.lastname: Casula
authors.forename: Saverio
authors.initials: S
authors.lastname: Moroni
authors.forename: Sandro
authors.initials: S
authors.lastname: Sorella
authors.forename: Claudia
authors.initials: C
authors.lastname: Filippi