Effect of Boundary Conditions on the Structure and Dynamics of Nanoscale Confined Water

In this paper, we investigate the effects of boundary structure on the properties of water in nanometer scale environments. We use molecular dynamic simulations to study water enclosed in model nanocavities with rigid boundaries of ice I(h) structure and compare its behavior to that of water in cavities with smooth structureless boundaries. We show the dependence of quantities such as velocity autocorrelation function and hydrogen-bond lifetimes on the size and surface characteristics of the cavity. The boundary structure greatly influences the structure and dynamics of the water. In the smallest systems considered, with dimensions of 3-8 A, the dynamics are slowed significantly, and the velocity autocorrelation function resembles that of solid ice.