If the wave function of the ground state is known exactly, then the VMC sampling will provide exact ground state properties. For example, in a system of hard-rods one has a knowledge of the ground state wave function and energy, but the correlation functions are not known. In this case the VMC calculation allows to complete the description of the system. In a similar manner if one knows exactly an eigenstate wave function, then the properties of the system can be obtained by the VMC sampling in an exact way.
The VMC can be effectively used for studying the metastable states. In particular one can make estimations of the critical parameters leading to the system collapse (see Sec. 6).
The VMC is used to optimize the variational parameters before doing DMC or FN-MC calculations, as the efficiency of the latter depends significantly on the quality of the trial wave function.