Pressure–temperature phase diagrams of selenium and sulfur in terms of Patashinski model

Abstract

The pressure -temperature phase diagrams of Se and S are calculated. Both melting and polymorphous phase transitions are described in frames of statistical Patashinski model. The results are in good agreement with experimental data of Brazhkin et. al.

New types of binary phase diagrams

“…Namely, the difference in the self energies of the clusters a of the first and the second types is necessary, since the relation between the numbers of those is no more fixed by the concentration of second component, as it was in previous case. As an example, the pressure-temperature phase diagram for the sulfur [9] is presented in Fig. 2.…”

“…To calculate the diagram, one needs the expression for thermodynamic potential as a function of p-impurity concentration, and c-the relative part of clusters of first structure in the rest material. This expression may be obtained by algebra presented in [8,9] and looks as follows:…”

Communication: Probable scenario of the liquid–liquid phase transition of SnI4

“…The model originally introduced by Patashinski et al 13 to consider melting phenomena, and later developed by Son et al 14 to discuss liquid-liquid phase transitions (LLPTs) is also worth being examined. The original model 13 is essentially a coarse-grained Potts model, and hence melting means losing the directional order among the Potts spins.…”

“…The original model 13 is essentially a coarse-grained Potts model, and hence melting means losing the directional order among the Potts spins. The extended model 14 is a type of mixed Potts model, consisting of an n-Potts system and an m-Potts system representing different local crystalline systems, which gives rise to a LLPT as a consequence of competition in melting of the two relevant ordered states. The latter correspond to the two crystalline phases separated by a solid-solid phase boundary.…”

“…The PS coarse-grained free energy is characterized by the two local order parameters representing the local structures in addition to the concentration x of the local structure of the first kind relative to that of the second. The mean-field (MF) treatment 14 for the local orders then leaves only x behind, the resultant free energy being virtually the one in the pBRS approximation. This is indeed the case and allows us to write the differences in the energy, entropy, and volume between the liquid states in terms of the parameters contained in the PS model as follows:…”