Showing papers by "Peter J. Rossky published in 1985"

A quantum mechanical study of structure in liquid H2O and D2O

Abstract: Path integral Monte Carlo methods are applied to the ST2 model of water to examine both the importance of quantum effects on the structure of liquid water and the differences in the structures of light and heavy water. Significant differences are apparent among the results for classical water, quantum H2O, and quantum D2O. For all quantities considered, the classical liquid is the most structured while quantum H2O is the least structured. The implications of these results for neutron and x‐ray diffraction experiments are examined; of the three atom–atom partial structure factors, the oxygen–oxygen function is found to be the most sensitive to quantum effects and the structural differences between light and heavy water appear to be large enough to be measured by x‐ray diffraction experiments.

The equilibrium solvation structure for the solvent‐separated hydrophobic bond

Abstract: We present a detailed geometrical analysis of the solvent in an aqueous solution containing two nonpolar atomic solutes which are constrained to an interatomic distance corresponding to a solvent‐separated free energy minimum. The results are obtained from a molecular dynamics simulation using ST2 water. The interpretation of structural features attributed to the hydrophobic effect are facilitated by a time averaging procedure which removes the high frequency librational excitation from the underlying liquid structure. Solvent reordering within the hydration shell surrounding the solutes is clearly revealed by octahedral resolution of orientational correlations and is consistent with the widespread view of ‘‘clathrate‐like’’ structure promotion induced by apolar moieties. Of particular interest, the relatively lengthy simulation reveals a rich variety of cage‐like solvation shell structures which encompass the solvent separated solute particles. The librational freedom of the shell molecules is briefly ex...

Theoretical studies of aqueous solution structure

Abstract: Computer simulation and, more analytical , integral equation methods can be applied to the problem of elucidating the detailed structural properties of strongly interacting molecular solutions of genuine chemical significance. The more analytical , extended RISM, approach can provide such results in a computationally convenient way not yet available via simulationS The success of such current statistical mechanical approaches in describing aqueous solutions is considered through three examples: the structure of liquid water as a function of hydrogen bond strength, the potential of mean force between atomic ions in an aqueous medium, and the aqueous solvent effect on the reaction free energy surface for the SN2 reaction of chloride with methylchloride.