Inhomogeneity effects on the structure and dynamics of water at the surface of a membrane: a computer simulation study.

The authors report the structural and dynamical properties of water interacting with the surface of a lipid bilayer. Three regions have been identified, which show different dynamical regimes of water: a region of strong water-solute interaction, a transition region, and the bulk water region. The dynamics of the strong-interacting water is dominated by caging effects, as shown by the analysis of the self-intermediate scattering function, and by the disrupture of water's hydrogen bond network, while the smooth transition to bulk water is traced back to the roughness of the bilayer surface.

Viscosity of liquid water from computer simulations with a polarizable potential model

The longitudinal and shear viscosity of water are calculated by molecular dynamics simulation with a polarizable potential model at room temperature. To overcome the difficulty of evaluating directly the stress autocorrelation function of a system with intrinsically many-body forces, we have resorted to the analysis of the wave-vector-dependent longitudinal and transverse-current correlation functions. In a memory function formalism, the generalized viscosity can be evaluated as a function of the wave vector k. By extrapolating to k=0, we find longitudinal and shear viscosity values in better agreement with the experimental value than the corresponding quantities evaluated by making use of a nonpolarizable potential model. This result points out that for a realistic reproduction of transport quantities, it is crucial to take into account many-body contributions to the interaction potential.

Instantaneous normal mode analysis of liquid HF

We present an instantaneous normal mode analysis of liquid HF aimed at clarifying the origin of peculiar dynamical properties which are supposed to stem from the arrangement of molecules in a linear hydrogen-bonded network. The present study shows that this approach is a unique tool for the understanding of the spectral features revealed in the analysis of both single molecule and collective quantities. For the system under investigation, we demonstrate the relevance of hydrogen-bonding "stretching" and fast librational motion in the interpretation of these features.