  In this paper we introduce a three-dimensional version of the Mercedes-Benz
model to describe water molecules. In this model van der Waals interactions and
hydrogen bonds are given explicitly through a Lennard-Jones potential and a
Gaussian orientation-dependent terms, respectively. At low temperature the
model freezes forming Ice-I and it reproduces the main peaks of the
experimental radial distribution function of water. In addition to these
structural properties, the model also captures the thermodynamical anomalies of
water: the anomalous density profile, the negative thermal expansivity, the
large heat capacity and the minimum in the isothermal compressibility.
