Investigating the Effective Potential Function of the Liquid Mercury on the Whole Liquid Range by Using the Internal Pressure

Mercury has the lowest critical temperature of any fluid metals.Therefore, it has been investigated experimentally with accuratemeasurements in the critical region [1]. The fundamental feature ofthe fluid metals is that the electronic structures of liquid and gasphases are completely different. Experimental data represent thatmercury near its triple point at densities larger than 11 g/cm3follows the nearly free electron theory of metals[2]. At lowerdensities 9 to 8 g/cm3, the cohesion mechanism of the atoms willbe suppressed by a partial localization of the valence electrons andthe metallic character is changed to a nonmetallic kind. The metalnonmetaltransition in liquid mercury is mainly due to lack ofoverlapping between the 6s and 6p bands [3, 4]. The major reasonfor the prediction of thermodynamic properties of mercury andother metals lie on the fact that the intermolecular interactionhighly depends on temperature and density. Density dependence ofmercury potential function has been subjected to the criticalinvestigations,12 by using the experimental structure factor andtheoretical modeling. In M-NMT region, there is no reliabletheoretical method to derive effective potential function for liquidmercury accurately. The accuracy of the theoretical studies on thethermodynamic properties of liquid metals is subjected to theaccuracy of the pair potential function describing theintermolecular interaction of these metals.The physical base of the internal pressure is a force tending toclose together the molecules that is intermolecular interactions [5].On the other hand, the experimental PVT data can be used tocalculate the internal pressure. Therefore, the experimental internalpressure is a good criterion for investigating the changes in theinter-atomic interactions.