Calculation of the transport and relaxation properties of methane. I. Shear viscosity, viscomagnetic effects, and self-diffusion

Abstract

Transport properties of pure methane gas have been calculated in the rigid-rotor approximation using the recently proposed intermolecular potential energy hypersurface [R. Hellmann et al., J. Chem. Phys. 128, 214303 (2008)] and the classical-trajectory method. Results are reported in the dilute-gas limit for shear viscosity, viscomagnetic coefficients, and self-diffusion in the temperature range of 80-1500 K. Compared with the best measurements, the calculated viscosity values are about 0.5% too high at room temperature, although the temperature dependence of the calculated values is in very good agreement with experiment between 210 and 390 K. For the shear viscosity, the calculations indicate that the corrections in the second-order approximation and those due to the angular-momentum polarization are small, less than 0.7%, in the temperature range considered. The very good agreement of the calculated values with the experimental viscosity data suggests that the rigid-rotor approximation should be very reasonable for the three properties considered. In general, the agreement for the other measured properties is within the experimental error.

Intermolecular potential energy surface and thermophysical properties of the CH4–N2 system

“…8 Thermophysical properties have also been calculated for a number of these PESs. 2,4,[6][7][8][9][10][11] In this work, we extend our recent studies of pure gases 2,4,[6][7][8][9][10][11] to binary CH 4 -N 2 mixtures. This system is sufficiently simple, on a molecular level, that the calculation of both the intermolecular PESs and of the thermophysical properties is computationally feasible.…”

“…1,[24][25][26][27][28][29][30] The accuracy and usefulness of this approach has been demonstrated for several pure molecular gases and atommolecule gas mixtures. 4,[6][7][8][9][10][11][31][32][33] In this paper, we limit our investigation of the transport properties to the shear viscosity and the binary diffusion coefficient. Results for the thermal conductivity will be reported separately, as they involve new theoretical developments that go beyond a simple validation of the intermolecular potential.…”

“…Accurate CH 4 -CH 4 and N 2 -N 2 potential functions are available and have been used to compute the second virial coefficients and transport properties of the pure gases. 2,6,9,10 Only three research groups have studied the CH 4 -N 2 pair potential using quantum-chemical ab initio calculations so far. The potential of Schindler et al 17 is based on supermolecular Hartree-Fock (HF) calculations with basis sets of triple-zeta quality for 21 points on the intermolecular PES.…”

Cross second virial coefficients and dilute gas transport properties of the (CH 4 + CO 2 ), (CH 4 + H 2 S), and (H 2 S + CO 2 ) systems from accurate intermolecular potential energy surfaces

“…Such calculations have been performed for a number of simple gases, such as methane [9,10], carbon dioxide [5], hydrogen sulfide [4,11], water vapor [12,13], or ethylene oxide [6], yielding transport property values with an uncertainty commensurate with the best experimental measurements over wide temperature ranges. We have recently extended the calculations to binary mixtures and have reported values for three traditional transport properties (viscosity, thermal conductivity, binary diffusion coefficient) and for the cross second virial coefficient of (CH 4 + N 2 ) mixtures [8,14].…”

“…We have previously developed such potentials [3][4][5] to investigate the thermophysical properties of these three pure gases [3][4][5][9][10][11].…”