An apparent critical point in binary mixtures of m-nitrotoluene with n-alkanes; experimental and simulation study

Abstract

We report a simulation study of the system m-nitrotoluene–n-decane, showing an apparent critical point, which lies in their metastable, experimentally inaccessible state, below their melting point, affecting physical and chemical properties of this systems in the stable liquid phase. The presence of the apparent critical point in this mixture has been experimentally observed by the non-linear dielectric effect (NDE) as an anomalous increase in the NDE values typical of critical concentrations. The phase diagrams of this mixture have evidenced that the system freezes in the homogenous phase and its melting point is higher than its critical temperature [M. Śliwińska-Bartkowiak, B. Szurkowski, T. Hilczer, Chem. Phys. Lett. 94 (1983) 609, M. Śliwińska-Bartkowiak, Ber. Bunsengess. Phys. Chem. 94 (1990) 64, M. Śliwińska-Bartkowiak, Phys. Lett. A 128 (1988) 84]. For such a system, we performed Monte Carlo simulations aimed at analyzing the kind of phase transition observed, and their conditions of their occurrence in a Lennard-Jones mixture. The enthalpy, configurational energy and radial distribution function have been estimated by the MC simulation method in the NPT system. Immiscibility conditions according to Hoheisel [M. Schoen, C. Hoheisel, Mol. Phys. 57 (1986) 65] approach have also been discussed.