Hydrogen Bond Properties and Dynamics of Liquid-Vapor Interfaces of Aqueous Methanol Solutions

The hydrogen bonded structure and dynamics of liquid-vapor interfaces of aqueous methanol solutions of varying compositions are investigated by means of molecular dynamics simulations. The dynamical aspects of the interfaces are investigated in terms of the single-particle dynamical properties such as the relaxation of velocity autocorrelation and the translational diffusion coefficients along the perpendicular and parallel directions and the dipole orientational relaxation of the interfacial water and methanol molecules and also in terms of the relaxation of water-water, water-methanol, and methanol-methanol hydrogen bonds at interfaces at 298 K. The results of the interfacial dynamics are compared with those of the corresponding bulk phases. The inhomogeneous density, anisotropic orientational profiles, surface tension, and the pattern of hydrogen bonding are calculated in order to characterize the location, width, microscopic structure, and the thermodynamic aspects of the interfaces and to explore their effects on the interfacial dynamical properties of water and methanol molecules.