QUANTUM SIMULATION OF WEAKLY-BOUND COMPLEXES USING DIRECT AB-INITIO ENERGY POINTS

We describe the use of a quantum diffusion Monte Carlo algorithm coupl ed directly to an ab initio program which supplies the (MP2) electroni c energy for the quantum simulation. This method does not require a fi t to a multidimensional potential energy surface. We demonstrate the a pplication of this method to (HF)(2) for which we have calculated the fully anharmonic zero-point energy, the ground state rotational consta nts, ro-vibrational wavefunctions and the tunnelling splitting. The me thod we describe is computationally demanding, but general, and will b e particularly attractive for use on parallel computers.