How dimensionality changes the anomalous behavior and melting scenario of a core-softened potential system?

Abstract

We present a computer simulation study of the phase diagram and anomalous behavior of two-dimensional (2D) and three-dimensional (3D) classical particles repelling each other through an isotropic core-softened potential. As in the analogous three-dimensional case, in 2D a reentrant-melting transition occurs upon compression under not too high pressure, along with a spectrum of thermodynamic and dynamic anomalies in the fluid phase. However, in two dimensions the order of the region of anomalous diffusion and the region of structural anomaly is inverted in comparison with the 3D case, where there exists a water-like sequence of anomalies, and has a silica-like sequence. In the low density part of the 2D phase diagram, melting is a continuous two-stage transition, with an intermediate hexatic phase. All available evidence supports the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario for this melting transition. On the other hand, at high density part of the phase diagram one first-order transition takes place.