PROPERTIES OF A STATISTICAL-MODEL OF ICE AT LOW-TEMPERATURES

A simple statistical model for ice is presented, based on a point charge model for H2O. To simulate this model, a Monte Carlo algorithm is constructed that samples proton configurations according to the Boltzmann distribution. The ground state of the model is numerically found to be an ordered nonferroelectric state with a unit cell of eight water molecules. The same structure has been previously proposed for the low-temperature phase of ice, called ice XI, on the basis of water-water potential calculations. The model is simulated at various temperatures, and the internal energy, entropy, and static dielectric constant are obtained as a function of the temperature. The model has a phase transition towards the ground state at T = 36 K, and no partial ordering is observed. This transition is compared with the phase transition towards ice XI in KOH-doped ice.