First-Principles Calculation of the Cross Second Virial Coefficient and the Dilute Gas Shear Viscosity, Thermal Conductivity, and Binary Diffusion Coefficient of the (H₂O + N₂) System

Abstract

The cross second virial coefficient and the low-density shear viscosity, thermal conductivity, and binary diffusion coefficient of mixtures of water (H2O) with nitrogen (N2) were obtained at temperatures of up to 2000 K with high accuracy employing statistical thermodynamics and the kinetic theory of polyatomic gases, respectively. The required intermolecular potential energy surface (PES) describing H2O–N2 interactions is presented in this work, while existing PESs from the literature were used to model H2O–H2O and N2–N2 interactions. All of the applied PESs are based on high-level quantum-chemical ab initio calculations. The values predicted for the investigated thermophysical properties agree satisfactorily with the existing experimental data and are probably the most accurate estimates currently available. Practical correlations of the cross second virial coefficient and the low-density binary diffusion coefficient, which are based exclusively on the calculated values, are also provided.

First‐Principles Diffusivity Ratios for Kinetic Isotope Fractionation of Water in Air

“…Regarding the work of Merlivat (1978), we note that her measured value for the absolute diffusivity of H 2 O in N 2 (which has a stated uncertainty of 1.6%) differs by only −0.9% from the calculated value (Hellmann, 2019a). The same approach used for H 2 O in N 2 and O 2 yields similar levels of agreement between theory and experiment for other gas pairs; for example, the best experimental data for the diffusivity of CO 2 in N 2 (with a stated uncertainty of less than 0.3%) agree within 0.2% with the first‐principles results of Crusius et al.…”

“…The present kinetic theory calculations are a direct extension of those performed recently by one of us for H 2 O in N 2 (Hellmann, 2019a) and H 2 O in O 2 and in air (Hellmann, 2020), which are based on new and highly accurate H 2 O–N 2 and H 2 O–O 2 pair potentials developed using state‐of‐the‐art quantum‐chemical ab initio approaches. We used these pair potentials without modification, thus assuming that isotopic substitution in the water molecule affects the collision dynamics mainly through the changes to the total molecular mass and to the moment of inertia tensor.…”

“…Table S2 of the supporting information lists the absolute diffusivities of H 2 O, HDO, , and in N 2 , O 2 , and air in the full investigated temperature range from 190 K to 2000 K and normalized to a pressure of 101.325 kPa (1 atm). Note that the diffusivities of H 2 O in N 2 , O 2 , and air from 250 K to 2000 K have previously been provided by Hellmann (2019a, 2020) and are only listed in Table S2 for convenience.…”

“…The intermolecular H 2 O–N 2 and H 2 O–O 2 potentials used in this study are available as Fortran 90 codes in the supporting information of Hellmann (2019a, 2020). Table S2 of the present supporting information provides the calculated diffusivities of H 2 O, HDO, , and in N 2 , O 2 , and air at a large number of temperatures from 190 to 2000 K. The data in Table S2 are also provided in the NIST Public Data Repository (https://doi.org/10.18434/M32271).…”

“…The intermolecular H 2 O-N 2 and H 2 O-O 2 potentials used in this study are available as Fortran 90 codes in the supporting information of Hellmann (2019aHellmann ( , 2020. Table S2 are also provided in the NIST Public Data Repository (https://doi.org/10.18434/M32271).…”