New developments in quantum Monte Carlo: calculation of forces
and optimized wave functions
Claudia Filippi, Department of Physics, National University of Ireland, Cork, Ireland
e-mail:claudia@monte3.ucc.ie
Jeudi, 2 mars 2000, 14h30
Two main stumbling blocks in quantum Monte Carlo (QMC), responsible
for the very slow development seen by QMC compared to density functional
theory (DFT), are the construction of the correlated wave function and
the computation of interatomic forces.
Relatively little attention has been given to the physical understanding
and numerical optimization of the antisymmetric part of the correlated
wave function, and, in practice, orbitals generated from other theoretical
approaches are used in the determinants in Jastrow-Slater wave functions.
As far as the forces, most QMC calculations have been performed on
geometries obtained with either DFT or conventional quantum chemistry
methods.
In this talk, I will discuss the techniques we have been developing
to address these difficulties. In particular, I will present a method
which provides an analog of the Hartree-Fock or multiconfiguration
self-consistent-field methods for correlated wave functions, when a
Jastrow correlation factor is present.
The method is feasible for atoms, molecules, and solids and is demonstrated
for the beryllium, carbon and neon atoms and for the solid diamond.
I will also discuss a novel correlated sampling method which efficiently
computes accurate forces within diffusion Monte Carlo and present its
application to first-row diatomic molecules.