Thermal expansivity of two-dimensional ice

The free energy components of crystalline forms of two-dimensional ice and a Lennard–Jones solid are calculated over a wide range of temperatures on the basis of the quasi-harmonic theory to examine whether the two-dimensional potential model is adequate to describe anomalous properties of low pressure ice. This enables us to evaluate a thermal expansivity from only the intermolecular interaction potential. It is found that the thermal expansivity of two-dimensional ice at low temperature is negative due to the negative mode Grüneisen parameters of low frequency modes while that of the Lennard–Jones solid is always positive.