Application of the m-6-8 potential to simple gases

Abstract

Publication costs assisted by the National Bureau of StandardsThe m-6-8 model potential function is applied to the gases argon, krypton, xenon, nitrogen, methane, and carbon dioxide and to the properties viscosity coefficient, self-diffusion coefficient, thermal conductivity coefficient, virial coefficient, and the isotopic thermal diffusion factor. The potential is shown to have a considerable advantage over previous simple analytic models in that it can satisfy two criteria: (a) it can be used to correlate a given property for all the gases studied over a wide temperature range with a single set of parameters, and (b) it can be used to correlate both transport and equilibrium properties for the monatomic gases with a single set of parameters. Reasons for the failure of polyatomic gases to satisfy (b) are suggested. A brief discussion on the relation of the potential to theory is given. (1) Work carried out at the National Bureau of Standards under the partial sponsorship of the Office of Standard Reference Data (for H. J. M. Hanley) and (for M. Klein), supported, in part, by the Air Force Command, Arnold Engineering Development Center, Tullahoma, Tenn. Delivery Order Number (40-600) 66-938 Program Element 61445014 AF Project 8951.(2) M. Klein and H. J. M. Hanley, J. Chem. Phys., 53, 4722 (1970).

First principles models of the interactions of methane and carbon dioxide

“…The Lennard-Jones potential, with the repulsion proportional to r −12 , is the most widely used because of its computational efficiency, but other potentials with exponential terms or several r −n terms are more accurate. For example, Klein and Hanley's m-6-8 potential [15,16] performs well for several thermodynamic properties over a wide range of temperatures. Here, we find that the Lennard-Jones potential makes the repulsive wall too steep for H-H or heavy atom-H interactions.…”

Spectral lineshapes of collision-induced absorption (CIA) and collision-induced light scattering (CILS) for molecular nitrogen using isotropic intermolecular potential. New insights and perspectives

“…In addition to the present potential, some older empirical Lennard-Jones [46,50,51], (m À 8-6) [52], ab initio potential [53] as well as the more recent ab initio potential of Hellmann [54] were considered.…”

“…Experimental second virial coefficients of nitrogen [19] Experimental second virial coefficients of nitrogen [20] Experimental second virial coefficients of nitrogen [21] Calculated second virial coefficients of nitrogen using BWLSL potential Calculated second virial coefficients of nitrogen using LJ(12-6) potential [46] Calculated second virial coefficients of nitrogen using LJ(12-6) potential [50] Calculated second virial coefficients of nitrogen using LJ (12-6) potential [51] Calculated second virial coefficients of nitrogen using (12-8-6) potential [52] Calculated second virial coefficients of nitrogen using ab initio potential [53] Calculated second virial coefficients of nitrogen using ab initio potential [54] T(K) B (cm 3 /mol) Eq. (10) is computed numerically if the atomic wavefunctions, which enter the computation of the matrix elements of the dipole moment, are obtained by numerical integration of the radial Schrö-dinger equation.…”

The self-diffusion coefficient of liquid methane

“…Further, effective spherical pair potentials were proposed for several molecules which were shown, via kinetic theory, to represent dilute gas transport properties to within experimental error [1,2]. In this paper the dilute gas calculations are extended to the dense gas and liquid.…”

“…The parameters m and y determine the strengths of interactions and an 1/r 8 attractive contribution to if(r), respectively. The selection of the parameters for a given fluid has been discussed in reference [2]. In particular, based on a fit of experimental dilute gas viscosity coefficients, we obtained for methane m= 11, y=3.0, r x 10 -11 m (or rmi n =4"101 x 10 -11m),…”