Exploration of Brueckner orbital trial wave functions in diffusion Monte Carlo calculations

Abstract

This study explores the utility of Brueckner orbitals as trial wave functions for diffusion Monte Carlo (DMC) calculations. Comparison is made with Hartree⿿Fock (HF) and density functional theory (DFT) orbitals allowing for an assessment of how well the three sets of orbitals describe the nodal surfaces. For the neutral test systems, PBE0 orbitals or Brueckner orbitals give DMC energies that are appreciably lower than those obtained using Hartree⿿Fock orbitals. For a CO2⿿ anion test case, a significantly lower DMC energy is obtained when using Brueckner orbitals rather than DFT orbitals as the trial function.