Melting curves and bulk moduli of the solid noble gasses He, Ne, Ar, Kr and Xe

Alternative bulk moduli for He, Ne, Ar, Xe and Kr, which differ from those reported in the literature, are presented. These alternative bulk moduli are based on the Gilvarry-Lindemann criterion, combined with a constraint demanding that the derived bulk moduli parameters will simultaneously fits the equations of state and the melting curves of these solid rare gasses. With increasing pressure, He, Ar, Xe and Kr exhibit a first order crystallographic phase transition from fcc to hcp structures. Ne is an exception and maintains the fcc phase up to 208 GPa. Good fits of the melting data are obtained by separately fitting each phase, allowing the extrapolation of the melting curves to higher pressures and temperatures. The anomalous linear behavior of the melting curve of Helium-4 is explained by assuming that the van der Waals attractive force should be added to the coulomb repulsion force when the distance between the two protons reduces under pressure. As the Grüneisen parameter γ is directly related to the bulk moduli B and B′, it is concluded that the flattening of the melting curves in the hcp region is absolutely dependent on the correct determination of the bulk moduli.