A model for the ice-vapor interface at equilibrium

We use a mean-field lattice-gas model to describe the equilibrium ice/vapor interface. The numerical values of the parameters in the model are taken from laboratory experiment and molecular dynamics calculations. The model predicts the existence at equilibrium of a layer of admolecules at the ice surface; it is only a few molecules thick because of the very strong water-water interactions. Sharp transitions in layer thickness occur at well-defined temperatures on each crystal face.