High-Pressure Melting Curves and Liquid-Liquid Phase Transition

Breaks on the melting lines in the pressure-temperature (T-m(P)) space are often handled as a hallmark of a liquid-liquid phase transition in pure materials. In this paper it is shown that there is no one-to-one agreement between these virtual breaks and liquid-liquid transitions. Four melting curves are analyzed; selenium, phosphorus, carbon and nitrogen. It is shown that a modified form of the Simon-Glatzel equation can describe experimental data, without introducing any break, demonstrating that the shape of the melting line is not an evidence for any further phase transition.