Characteristic Curves of the Mie Fluid

Abstract

Brown's characteristic curves of the Mie n,m fluid were investigated using molecular dynamics (MD) simulation and a molecular-based equation of state. Both, the 0th-order (Zeno) and three 1st-order characteristic curves (Amagat, Boyle, and Charles) were studied. The study was carried out using a hybrid approach combining MD simulation and molecular theory. Thereby, exact values for the zero-density limit of the characteristic curves were obtained using the second virial coefficient route. The focus was on the variation of the repulsive exponent of the Mie potential with n=8,10,11,12,13,14,16,20,36,48 (dispersive exponent constant at m=6). Also, the influence of the dispersive exponent on the characteristic curves was studied with m=4,5,6,7,8 (repulsive exponent constant at n=12). In total, 14 Mie fluids were studied. Based on the results, the influence of the shape of the intermolecular potential on the macroscopic properties, i.e. the characteristic curves, is elucidated. Interestingly, the Amagat curve is found to exhibit a peculiar dependency on the repulsive exponent. However, the postulates of Brown regarding the form and regularities of the characteristic curves are confirmed for all studied Mie fluids. Furthermore, the applicability of the classical corresponding states principle is assessed using the characteristic curve data. Important differences are obtained for the two exponents: The corresponding states principle captures reasonably well the variation of the dispersive exponent, but fails for describing the influence of the repulsive exponent. The results from this work are compared with predictions from a molecular-based equation of state, which is found to perform well in almost all studied cases.