Monte Carlo simulation of small hydrate clusters of NOminus;2

摘要

The groundhyphen;state Hartreendash;Fock (HF) potential for the NOminus;2:H2O dimer has been computed for 102 different intermolecular geometrical configurations and has been expressed in a computationally convenient analytical form. The main conclusion drawn from these calculations is that the ionndash;solvent attraction is mainly electrostatic for intermolecular distances between 6.0 and 7.0 bohr (Nhyphen;tohyphen;O distance). Keeping the dipole vector of the H2O molecule oriented toward the NOminus;2ion yields energetically favorable conformations. Rotations of the H2O molecule which do not change the dipole orientation of the H2O have been found to have small barriers (sim;4 kcal/mole), whereas those that destroy proper dipole alignment encounter large (sim;30 kcal/mole) barriers. The use of such ionndash;H2O intermolecular potentials together with the H2O:H2O pair potential of Clementi permits Monte Carlo techniques to be used to examine the nature of the inner hydration shells of NOminus;2. The results of Monte Carlo simulations of NOminus;2(H2O)n1les;nles;15 are discussed in some detail.