Diffusion Monte Carlo provides a powerful general tool for evaluating the ground state energy and wave function based on a Hamiltonian.  It is particularly useful for studies involving the do-vibrational ground state of molecules that undergo large amplitude motions even at their zero-point level.  Over the past decade, we have applied this technique to studies involving molecules including CH5+, H5+, H5O2+ and H3O2-.  Recently we have begun to explore rotation-vibration mixing in such molecules.  In this talk, we will present two approaches for evaluating rotationally excited states.  In the first, we employ the same fixed-node approach that has been effective for vibrationally excited states.  In the second, we describe rotational part of the wave function in a basis set based on a model Hamiltonian that provides a good zero-order description of the rotations.   Results of these studies for H3+, CH5+ and H5+ will be presented.

Diffusion Monte Carlo studies of rotation-vibration energies and wave functions for molecules that undergo large amplitude vibrational motions

248th National Meeting (2014)

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