Phase transitions in the Gaussian core system

Some aspects of phase transition behavior have been studied for a classical system of particles which interact in pairs via repelling Gaussian potentials. In a specific low-temperature, low-density limit, this model acts as though it were composed of rigid spheres. Study of lattice sums suggests that at T=0, a fcc crystal stable at low density transforms under compression to a bcc crystal. It is shown that sufficient compression at any fixed T≳0 always produces a fluid phase. Under suitable temperature and density conditions, the model can exhibit positive, negative, or vanishing volumes of melting.