LIQUID BENZENE CONFINED BETWEEN GRAPHITE SURFACES - A CONSTANT-PRESSURE MOLECULAR-DYNAMICS STUDY

We derive expressions for the internal and external stress tensor for a molecular system which is periodic in two dimensions and confined by an external potential along the third dimension. Based on the externa l pressure, we propose an extended-phase-space constant pressure molec ular dynamics simulation method. We apply this method to simulations o f liquid benzene confined between two graphite surfaces. The intramole cular interactions are thereby adopted from the AMBER force field, whe reas the liquid-surface interaction is described in terms of a static external potential acting on the benzene molecules. Our results test t he method and provide a molecular picture of the surface induced struc ture of the liquid as well as its dynamical behavior near the surface. We find that the surface affects the structure of the liquid on a len gth scale significantly larger than the direct range of the liquid-sur face potential. Additionally, we observe a fast exchange of benzene mo lecules between the first and second liquid layer adjacent to the surf ace.