Anisotropic intracule densities and electron correlation in H_2:A quantum Monte Carlo study

摘要

We derive efficient quantum Monte Carlo estimators for the anisotropic intracule and extraculedensities. These estimators are used in conjunction with an accurate explicitly correlated wavefunction to investigate the bond-length dependence of electron correlation effects in the ground-stateH_2molecule. It is shown that the localized increase in magnitude of the correlation energy as thebond is stretched is accompanied by highly anisotropic correlation effects. In addition, we find asmall long-range part of the Coulomb hole, which is present even at the equilibrium bond length.