Adiabatic diffusion Monte Carlo approaches for studies of ground and excited state properties of van der Waals complexes

Several adiabatic extensions to the diffusion Monte Carlo approach are presented. In the first, an adiabatic form of the finite field method is developed for the systematic evaluation of expectation values. In addition, an adiabatic flexible node method for calculating excited states is described. The above methods are applied to NeSH and Ar2HCl where comparisons to results of variational calculations can be made.