Alexandre Kollias, Berkeley

Mercredi, 7 décembre 2005, 15 h 30,
salle 1, Bâtiment St.Raphael, 3 rue Galilée, 94200 Ivry-sur-Seine
Recent progress in the development and application of zero-variance force estimators will be presented. The discussion will include effective-core potential (ECP) and all-electron estimators for the variational Monte Carlo (VMC) and fixed-node diffusion Monte Carlo (DMC) methods. VMC and DMC results will focus on LiH as a model system, to elucidate the differences in the ECP and all-electron forces; in particular the difficulties encountered for ECP force estimators.
In addition, progress on all-electron trial functions will be presented demonstrating improved results, both at the Hartree-Fock and VMC levels. This improvement is achieved by fitting a large number of contacted Gaussian functions to Slater basis functions. As a result, an increase in computational efficiency for QMC is achieved, both in speed and reduction of error bars. Finally, possible application of these all- electron trial functions to obtain zero-variance energy estimators will be discussed.