Structure and dynamics of nonaqueous mixtures of dipolar liquids. II. Molecular dynamics simulations

Molecular dynamics simulations have been used to study mixtures of acetone/methanol, acetonitrile/ methanol, and acetone/acetonitrile over their entire composition range. Using the effective pair potentials of the neat liquids, the simulations reproduce much of the experimental spectra presented in the previous paper @D. S. Venables, A. Chiu, and C. A. Schmuttenmaer, J. Chem. Phys. 113, 3243 ~2000!#. In addition to the total dipole spectra, autocorrelation functions and their corresponding spectra were calculated for the single dipole moment as well as the translational and rotational velocities of each component in the mixtures. Radial and spatial distribution functions, hydrogen bonding, and methanol chain formation in the mixtures were also analyzed. The red-shift of the high frequency librational band is attributed to methanol chains breaking up into shorter segments, and to hydrogen bonding between methanol and co-solvent molecules. Methanol molecules have a strong tendency to reside in chains, even at low methanol concentrations, and hydrogen bonding is the primary determinant of structure in the mixtures. © 2000 American Institute of Physics. @S0021-9606~00!51432-9#