Ab initio potential energy surface for the nitrogen molecule pair and thermophysical properties of nitrogen gas

作者：Hellmann Robert^*

来源：Molecular Physics, 2013, 111(3): 387-401.

DOI：10.1080/00268976.2012.726379

• nitrogen pair potential
• ab initio calculations
• kinetic theory
• virial coefficients
• transport properties

A four-dimensional potential energy hypersurface (PES) for the interaction of two rigid nitrogen molecules was determined from high-level quantum-chemical ab initio computations. A total of 408 points for 26 distinct angular configurations were calculated utilizing the counterpoise-corrected supermolecular approach at the CCSD(T) level of theory and basis sets up to aug-cc-pV5Z supplemented with bond functions. The calculated interaction energies were extrapolated to the complete basis set limit and complemented by corrections for corecore and corevalence correlations, relativistic effects and higher coupled-cluster levels up to CCSDT(Q). An analytical sitesite potential function with five sites per nitrogen molecule was fitted to the interaction energies. The PES was validated by computing second and third pressure virial coefficients as well as shear viscosity and thermal conductivity in the dilute-gas limit. An improved PES was obtained by scaling the CCSDT(Q) corrections for all 408 points by a constant factor, leading to quantitative agreement with the most accurate experimental values of the second virial coefficient over a wide temperature range. The comparison with the best experimental data for shear viscosity shows that the values computed with the improved PES are too low by about 0.3% between 300 and 700K. For thermal conductivity large systematic deviations are found above 500K between the calculated values and most of the experimental data.

• 出版日期2013-2-1