(204h) Molecular-Inspired Parameters Concealed in the Van Der Waals Attractive Force Revealed By First Principles, Statistical Mechanics and Perturbation Methods

Although it is universally known and still actively published that the Van der Waals (VDW) theory predicts inaccurate liquid density, incorrect heat capacity, unreliable for highly polar and hydrogen-bonded fluids, incorrect at gas-liquid critical point, inaccurate for large components and incapable of accurate virial coefficients; but as of yet, it has not been widely reported that those fluid properties largely depend on the molecular structure of pure substances which is evidently not reflected by the semi-empirical parameters in the VDW 1873 theory. By contrast to the fundamental equation which has no mathematical form and in lieu of the complete development of molecular theory comparable to the kinetic theory of gases or the ordered-crystal lattice of solids, the VDW 1873 equation has been reformulated as a broad generic cubic equation by using four physical parameters that reflect molecular attraction, size, structure and shape for asymmetric pure substances. Those discovered molecular-inspired parameters are achieved by expressing the VDW molecular properties (Z_c, Ω_w, Ω_a, Ω_b) in terms of the two parameters in the formulated generic equation of state and molecular interpretation of the two parameters are performed by first principles, statistical mechanics and perturbation-sensitivity inspired techniques. In contrast to the assumptions in the textbooks, the VDW intuitive attractive force is shown to have molecular significance. The versatility of the formulated generic cubic equation is demonstrated by predicting virial coefficients, coexistence gas-liquid properties as well as estimated gas-liquid critical-point properties for thermodynamic, thermophysical and transport properties.