文摘
The accuracy of total electronic energies obtained using the fixed-node diffusion quantum Monte Carlo (FN-DMC) method is determined by the choice of the many-body nodal surface. Here, we perform a systematic comparison of the quality of FN-DMC energies for a selection of atoms and diatomic molecules using nodal surfaces defined by single determinants of Hartree鈥揊ock, B3LYP, and LDA orbitals. Through comparison with experimental results, we show that the use of Kohn鈥揝ham orbitals results in significantly improved FN-DMC atomization energies over those obtained using Hartree鈥揊ock orbitals. We also discuss the effect of spin contamination in the orbitals.