Hypothesis for coordination number of critical fluid molecules expressed in model potential and critical temperature for simple substances

Abstract

An easy model of the critical state of simple substances, which can be considered as Lennard-Jones gases, is proposed. It is based on a hypothesis for the first coordination number of molecules in minimally bound infinite clusters. This model, together with any theoretical approach describing the intermolecular interactions, leads to express the relationships between parameters of molecules and critical temperature. One of the most effective approaches to describe van der Waals energy—the theory of generalized charges is applied in this paper. For the main elements of the 7th and 8th groups of the periodic table, the non-empirical calculations of the intermolecular interaction energy and critical temperature have been carried out. Moreover, a priori predictions of unknown values for 85At and 86Rn have been made, too. Theoretical estimates by the model are in agreement with the experimental data that is the confirmation of the hypothesis put forward.