Quantum simulation of the benzene-water complex

A theoretical investigation is presented of the weakly bound complex formed between benzene and water. Diffusion quantum Monte Carlo methods are used to describe the nuclear motion plus two potentials which give quite good agreement with DZP/MP2 ab initio calculations, and simulations were performed for four isotopomers of C6H6 ⋯ H2O. Although the minimum energy structure can be considered to have only a single hydrogen bond, vibrational averaging renders the hydrogens indistinguishable, a prediction in agreement with the experimental observation that the complex is a symmetric top. The results include zero-point energies, vibrationally averaged structures, rotational constants and wavefunctions. By calculating transition states and rearrangement mechanisms, it is possible to characterize the tunnelling dynamics and calculate the associated tunnelling splittings