Quantum Monte Carlo for molecules: Green's function and nodal release

A random walk algorithm is presented which exactly calculates the properties of a many-electron system. For that purpose both the Green's function Monte Carlo method and nodal relaxation have been employed and both are described in detail. The scheme is applied to several small molecules, (H ₃, LiH, Li₂, H₂O) and with modest computational effort and simple importance functions, ground state energies are obtained which agree with experimental energies within statistical error bars. The small energy decrease due to nodal release is accurately evaluated by a difference method.