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Mass dipole contribution to the isotopic Soret effect in molecular mixtures
File(s)
SI_ORGandFB.pdf (743.68 KB)
Supporting information
114503_1_5.0164253.pdf (13.44 MB)
Published version
Author(s)
Gittus, Oliver R
Bresme, Fernando
Type
Journal Article
Abstract
Temperature gradients induce mass separation in mixtures in a process called thermal diffusion and are quantified by the Soret coefficient ST. Thermal diffusion in fluid mixtures has been interpreted recently in terms of the so-called (pseudo-)isotopic Soret effect but only considering the mass and moment of inertia differences of the molecules. We demonstrate that the first moment of the molecular mass distribution, the mass dipole, contributes significantly to the isotopic Soret effect. To probe this physical effect, we investigate fluid mixtures consisting of rigid linear molecules that differ only by the first moment of their mass distributions. We demonstrate that such mixtures have non-zero Soret coefficients in contrast with ST = 0 predicted by current formulations. For the isotopic mixtures investigated in this work, the dependence of ST on the mass dipole arises mainly through the thermal diffusion coefficient DT. In turn, DT is correlated with the dependence of the molecular librational modes on the mass dipole. We examine the interplay of the mass dipole and the moment of inertia in defining the isotopic Soret effect and propose empirical equations that include the mass dipole contribution.
Date Issued
2023-09-21
Date Acceptance
2023-08-03
Citation
Journal of Chemical Physics, 2023, 159 (11), pp.1-15
URI
URL
DOI
ISSN
0021-9606
Publisher
American Institute of Physics
Start Page
1
End Page
15
Journal / Book Title
Journal of Chemical Physics
Volume
159
Issue
11
Copyright Statement
© 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/37724736
Publication Status
Published
Coverage Spatial
United States
Article Number
114503
Date Publish Online
2023-09-19