Firstprinciples binary diffusion coefficients for H, H _{2} and four normal alkanes + N _{2}
Collision integrals related to binary (dilute gas) diffusion are calculated classically for six species colliding with N _{2}. The most detailed calculations make no assumptions regarding the complexity of the potential energy surface, and the resulting classical collision integrals are in excellent agreement with previous semiclassical results for H + N _{2} and H _{2} + N _{2} and with recent experimental results for C _{n} H _{2n+2} + N _{2}, n = 2–4. The detailed classical results are used to test the accuracy of three simplifying assumptions typically made when calculating collision integrals: (1) approximating the intermolecular potential as isotropic, (2) neglecting the internal structure of the colliders (i.e., neglecting inelasticity), and (3) employing unphysical R ^{–12} repulsive interactions. The effect of anisotropy is found to be negligible for H + N _{2} and H _{2} + N _{2} (in agreement with previous quantum mechanical and semiclassical results for systems involving atomic and diatomic species) but is more significant for larger species at low temperatures. For example, the neglect of anisotropy decreases the diffusion coefficient for butane + N _{2} by 15% at 300 K. The neglect of inelasticity, in contrast, introduces only very small errors. Approximating the repulsivemore »
 Authors:

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 Sandia National Lab. (SNLCA), Livermore, CA (United States)
 Argonne National Lab. (ANL), Argonne, IL (United States)
 Publication Date:
 Report Number(s):
 SAND20150160J
Journal ID: ISSN 00219606; JCPSA6; 560415; TRN: US1600393
 Grant/Contract Number:
 AC0494AL85000
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of Chemical Physics
 Additional Journal Information:
 Journal Volume: 141; Journal Issue: 12; Journal ID: ISSN 00219606
 Publisher:
 American Institute of Physics (AIP)
 Research Org:
 Sandia National Lab. (SNLCA), Livermore, CA (United States)
 Sponsoring Org:
 USDOE National Nuclear Security Administration (NNSA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 74 ATOMIC AND MOLECULAR PHYSICS; anisotropy; diffusion; intermolecular potentials; combustion; potential energy surfaces
 OSTI Identifier:
 1237364
Jasper, Ahren W., Kamarchik, Eugene, Miller, James A., and Klippenstein, Stephen J.. Firstprinciples binary diffusion coefficients for H, H2 and four normal alkanes + N2. United States: N. p.,
Web. doi:10.1063/1.4896368.
Jasper, Ahren W., Kamarchik, Eugene, Miller, James A., & Klippenstein, Stephen J.. Firstprinciples binary diffusion coefficients for H, H2 and four normal alkanes + N2. United States. doi:10.1063/1.4896368.
Jasper, Ahren W., Kamarchik, Eugene, Miller, James A., and Klippenstein, Stephen J.. 2014.
"Firstprinciples binary diffusion coefficients for H, H2 and four normal alkanes + N2". United States.
doi:10.1063/1.4896368. https://www.osti.gov/servlets/purl/1237364.
@article{osti_1237364,
title = {Firstprinciples binary diffusion coefficients for H, H2 and four normal alkanes + N2},
author = {Jasper, Ahren W. and Kamarchik, Eugene and Miller, James A. and Klippenstein, Stephen J.},
abstractNote = {Collision integrals related to binary (dilute gas) diffusion are calculated classically for six species colliding with N2. The most detailed calculations make no assumptions regarding the complexity of the potential energy surface, and the resulting classical collision integrals are in excellent agreement with previous semiclassical results for H + N2 and H2 + N2 and with recent experimental results for C n H2n+2 + N2, n = 2–4. The detailed classical results are used to test the accuracy of three simplifying assumptions typically made when calculating collision integrals: (1) approximating the intermolecular potential as isotropic, (2) neglecting the internal structure of the colliders (i.e., neglecting inelasticity), and (3) employing unphysical R–12 repulsive interactions. The effect of anisotropy is found to be negligible for H + N2 and H2 + N2 (in agreement with previous quantum mechanical and semiclassical results for systems involving atomic and diatomic species) but is more significant for larger species at low temperatures. For example, the neglect of anisotropy decreases the diffusion coefficient for butane + N2 by 15% at 300 K. The neglect of inelasticity, in contrast, introduces only very small errors. Approximating the repulsive wall as an unphysical R–12 interaction is a significant source of error at all temperatures for the weakly interacting systems H + N2 and H2 + N2, with errors as large as 40%. For the normal alkanes in N2, which feature stronger interactions, the 12/6 Lennard–Jones approximation is found to be accurate, particularly at temperatures above –700 K where it predicts the fulldimensional result to within 5% (although with somewhat different temperature dependence). Overall, the typical practical approach of assuming isotropic 12/6 Lennard–Jones interactions is confirmed to be suitable for combustion applications except for weakly interacting systems, such as H + N2. For these systems, anisotropy and inelasticity can safely be neglected but a more detailed description of the repulsive wall is required for quantitative predictions. Moreover, a straightforward approach for calculating effective isotropic potentials with realistic repulsive walls is described. An analytic expression for the calculated diffusion coefficient for H + N2 is presented and is estimated to have a 2sigma error bar of only 0.7%.},
doi = {10.1063/1.4896368},
journal = {Journal of Chemical Physics},
number = 12,
volume = 141,
place = {United States},
year = {2014},
month = {9}
}