First-Principles Diffusivity Ratios for Kinetic Isotope Fractionation of Water in Air
Publication date
2020-09-28
Document type
Research article
Author
Harvey, Allan H.
Organisational unit
Scopus ID
Series or journal
Geophysical Research Letters
Periodical volume
47
Periodical issue
18
Peer-reviewed
✅
Part of the university bibliography
✅
Language
English
Keyword
Diffusion
First-principles calculations
Isotope fractionation
Kinetic theory
Water
Abstract
Kinetic isotope fractionation between water vapor and liquid water or ice depends on the ratio of the diffusivities of the isotopic species in air, but there is disagreement as to the values of these ratios and limited information about their temperature dependence. We use state-of-the-art intermolecular potential-energy surfaces for the water-nitrogen and water-oxygen pairs, along with the kinetic theory of molecular gases, to calculate from first principles the diffusivities of water isotopologues in air. The method has sufficient precision to produce accurate diffusivity ratios. For the HDO/H2O ratio, we find that the often used hard-sphere kinetic theory is significantly in error and confirm the 1978 experimental result of Merlivat. For the ratios involving 17O and 18O, the simple kinetic theory is relatively close to our more rigorous results. We provide diffusivity ratios from 190 K to 500 K, greatly expanding the range of temperatures for which these ratios are available.
Version
Not applicable (or unknown)
Access right on openHSU
Metadata only access
Open Access Funding
Wiley (DEAL)