Investigation of the Anomalous Behavior of the Density and Thermal Expansion in a Two-Dimensional System with the Hertz Potential

A two-dimensional system characterized by the Hertz potential with the parameter α = 7/2 in the region of crystal-phase stability has been studied by the molecular dynamics method. It is shown that the anomaly of the density and thermal expansion, found previously for this system in the equation of state along isochores, also manifests itself on isotherms. A study of the translational and orientational order parameters revealed their drop in the density anomaly region, which is most pronounced for the translational order parameter. The obtained results are also in good agreement with the previous data on the attenuation of the transverse phonon mode in this region. This correlation indicates the presence of a strongly diffuse isostructural transformation in the anomalous region of the phase diagram.