Zero-point energy constrained quasiclassical, classical, and exact quantum simulations of isomerizations and radial distribution functions of the water trimer using an ab initio potential energy surface

A recently suggested constrained quasiclassical trajectory (c-QCT) method for avoiding the zero-point leak in the water dimer [11] is applied to the water trimer, employing an ab initio full-dimensional potential energy surface. We demonstrate the failure of the standard/unconstrained QCT method for (H2O)(3) and show the utility of c-QCT dynamics. In addition, standard classical molecular dynamics and c-QCT dynamics are contrasted for the time-dependence of isomerizations between the multiple global and local minima as well as radial distribution functions are obtained at low temperature and at 300 K. Results from these calculations are compared with rigorous quantum path integral Monte Carlo calculations. (C) 2010 Elsevier B.V. All rights reserved.