Liquid-vapour interfaces of aqueous trimethylamine-N-oxide solutions: A molecular dynamics simulation study

The liquid-vapour interfaces of aqueous trimethylamine-N-oxide (TMAO) solutions of varying composition are investigated by means of molecular dynamics simulations. The inhomogeneous density, anisotropic orientational profiles, surface tension and the pattern of hydrogen bonding are calculated in order to characterize the location, microscopic structure and the thermodynamic aspects of the interfaces and to explore their effects on the interfacial dynamical properties of water and TMAO molecules. 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 of the interfacial water and TMAO molecules at 298 K. The results of the interfacial dynamics are compared with those of the corresponding bulk phases.