Volumetric anomaly of a Gaussian core fluid on a sphere

The thermodynamic and structural properties of the Gaussian-core model, with particular emphasis on its volumetric behaviour, have been investigated in two dimensions in a system of particles moving on a sphere. The absence of an attractive term in the potential rules out the liquid-vapour phase transition while the curvature of the host surface inhibits the formation of a long-range-ordered crystalline arrangement. We found that the density exhibits, at moderate pressures, two extrema which delimit the temperature range where the thermal expansivity attains negative values. The presence of a density minimum has also beendetected in the two-dimensional crystal on a plane.