QUANTUM SIMULATION OF THE BENZENE-WATER COMPLEX

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