Gibbs energy of polymeric liquid phosphorus (liquid 2) as well as molar volumes and bulk moduli of both liquid phosphorus phases were found by solving the inverse problem using literature data on melting of orthorhombic phosphorus . However, during the optimization process we used only slopes of two branches of the melting curve (Fig. ), and not the absolute temperature values because melting temperature of orthorhombic phosphorus at ambient pressure reported in (980 K) is overstated by 100 K compared to the generally accepted value of 883 K . The results obtained show that the low-pressure liquid phase (liquid 1) has 33% higher volume than the highpressure liquid phase (liquid 2) which is in agreement with results of ab initio quality molecular dynamics simulation of liquid phosphorus under pressure . Besides, bulk modulus of liquid 1 was found to be significantly lower than that of liquid 2 (see Table ).