6 research outputs found
Deconstructing classical water models at interfaces and in bulk
Using concepts from perturbation and local molecular field theories of
liquids we divide the potential of the SPC/E water model into short and long
ranged parts. The short ranged parts define a minimal reference network model
that captures very well the structure of the local hydrogen bond network in
bulk water while ignoring effects of the remaining long ranged interactions.
This deconstruction can provide insight into the different roles that the local
hydrogen bond network, dispersion forces, and long ranged dipolar interactions
play in determining a variety of properties of SPC/E and related classical
models of water. Here we focus on the anomalous behavior of the internal
pressure and the temperature dependence of the density of bulk water. We
further utilize these short ranged models along with local molecular field
theory to quantify the influence of these interactions on the structure of
hydrophobic interfaces and the crossover from small to large scale hydration
behavior. The implications of our findings for theories of hydrophobicity and
possible refinements of classical water models are also discussed
Application of molecular simulations: Insight into liquid bridging and jetting phenomena
Molecular dynamics simulations have been performed on pure liquid water, aqueous solutions of sodium chloride, and polymer solutions exposed to a strong external electric field with the goal to gain molecular insight into the structural response to the field. Several simulation methodologies have been used to elucidate the molecular mechanisms of the processes leading to the formation of liquid bridges and jets (in the production of nanofibers). It is shown that in the established nanoscale structures, the molecules form a chain with their dipole moments oriented parallel to the applied field throughout the entire sample volume. The presence of ions may disturb this structure leading to its ultimate disintegration into droplets; the concentration dependence of the threshold field required to stabilize a liquid column has been determined. Conformational changes of the polymer in the jetting process have also been observed