Electron pair properties for the helium atom from explicitly correlated wave functions

Starting from a compact and accurate explicitly correlated wave function a systematic study of two-body properties in both position and momentum space has been performed for the He atom. A systematic comparison with the values obtained from both a multi-configuration Hartree–Fock and a Hylleraas (when available) wave function is performed. The wave function and the different expectation values are obtained by using the variational Monte Carlo method. The quality of both the wave function and the methodology used are analyzed and discussed.