Title: Computational study of structural and thermodynamic properties of binary nanoclusters and hydrogen gas in liquid water Speaker: Dubravko Sabo, Sandia National Laboratories Date/Time: Tuesday, March 4, 2008, 9:30-10:30am Location: CSRI Building, Room 90 (Sandia NM) Brief Abstract: Structural and thermodynamic properties are investigated for one of the simplest hydrophobic solutes, a hydrogen molecule solvated in liquid water. The structural properties are calculated using different representations of the intermolecular interactions within molecular dynamics, Monte Carlo and ab initio molecular dynamics simulation frameworks. Although structural details differ in the radial distribution functions obtained by different force fields all approaches agree that 16 water molecules coordinate hydrogen. The thermodynamic properties are investigated using Monte Carlo molecular simulation and the quasichemical theory of liquids. Results show that the net hydration free energy arises from a balance between chemical association and molecular packing. Additionally, the results suggest the molecular packing is almost equally driven by unfavorable enthalpic and entropic components. In the second part of this presentation we present studies of the structural and thermodynamic properties of selected binary Lennard-Jones 13 atom clusters. The effect of adding selected impurity atoms to a homogeneous cluster is explored. We analyze the energy landscape of the studied systems using disconnectivity graphs. We show that it is possible to controllably induce new structures as well as reorder and stabilize existing structures that are characteristic of higher-lying minima. The thermal properties, such as total energy and heat capacity, are calculated as a function of temperature by using the classical and path integral Monte Carlo methods combined with the parallel tempering technique. A modification in the phase change phenomena from the presence of impurity atoms and nuclear quantum effects are investigated.CSRI POC: John Aidun, (505) 844-1209 |