A diffusion quantum Monte Carlo method based on floating spherical Gaussian orbitals and Gaussian geminals: Dipole moment of lithium hydride molecule

Abstract

A diffusion quantum Monte Carlo method, based on a trial wave function, built from floating spherical Gaussian orbitals and geminals, is reported. The ability to precisely sample the Gaussian function by using the Ornstein–Uhlenbeck random walks process, to treat electron correlation effect explicitly, and to apply the Hellmann–Feynman theorem are the important consequences of this approach. Floating functions, which remedy deficiency of electron density around nuclei, satisfy the Hellmann–Feynman theorem. Gaussian geminals, which correlate the electron pair directly, are used to treat correlation energy and to improve the quality of the trial wave function. Applying this type of trial wave function, within fixed-node approximation, in diffusion quantum Monte Carlo (QMC) calculation of ground state energies of lithium hydride molecule, provides very good estimates of the electronic energy and dipole moment. We also compare the results with several previous QMC results and experiments.