Construction of phase diagrams to estimate phase transitions at high pressures: A critical point at the solid liquid transition for benzene.

Phase diagrams are an integral part of the estimation of material properties in the case of high temperature and pressure. The pressure-temperature (P-T) phase diagram is used to determine the state of aggregation (solid, liquid, gaseous) of a substance under given conditions. This article presents a method to reveal new states in the phase diagram, including the possibility of the plasma state. Using the empirical data of benzene, a critical pressure beyond solid-liquid equilibrium was estimated. It is highly probable that beyond these pressures, benzene may ionize and exhibit plasma behavior. The method proposed in this work for benzene could also be applied to create a comprehensive phase diagram of Hydrogen at certain pressure and temperature. Because the complex behavior of hydrogen, as well as the constant discovery of new varieties and the creation of many different phases of hydrogen makes it very difficult to construct a realistic phase diagram. [Display omitted] • The critical pressure is the highest pressure that a solid-liquid coexists. • Beyond critical pressure, matters may ionize and exhibit plasma behavior. • The plasma state of the matter should be included in the phase diagram. • Graphic method can be used to find critical points of a matter. [ABSTRACT FROM AUTHOR]