State-of-the-art ab initio potential energy curve for the krypton atom pair and thermophysical properties of dilute krypton gas

Abstract

A new reference krypton-krypton interatomic potential energy curve was developed by means of quantum-chemical ab initio calculations for 36 interatomic separations. Highly accurate values for the interaction energies at the complete basis set limit were obtained using the coupled-cluster method with single, double, and perturbative triple excitations as well as t-aug-cc-pV5Z and t-aug-cc-pV6Z basis sets including mid-bond functions, with the 6Z basis set being newly constructed for this study. Higher orders of coupled-cluster terms were considered in a successive scheme up to full quadruple excitations. Core-core and core-valence correlation effects were included. Furthermore, relativistic effects were studied not only at a scalar relativistic level using second-order direct perturbation theory, but also utilizing full four-component and Gaunt-effect computations. An analytical pair potential function was fitted to the interaction energies, which is characterized by a depth of 200.88 K with an estimated standard uncertainty of 0.51 K. Thermophysical properties of low-density krypton were calculated for temperatures up to 5000 K. Second and third virial coefficients were obtained from statistical thermodynamics. Viscosity and thermal conductivity as well as the self-diffusion coefficient were computed using the kinetic theory of gases. The theoretical results are compared with experimental data and with results for other pair potential functions from the literature, especially with those calculated from the recently developed ab initio potential of Waldrop et al. [J. Chem. Phys. 142, 204307 (2015)]. Highly accurate experimental viscosity data indicate that both the present ab initio pair potential and the one of Waldrop et al. can be regarded as reference potentials, even though the quantum-chemical methods and basis sets differ. However, the uncertainties of the present potential and of the derived properties are estimated to be considerably lower.

Modeling of transport phenomena in gases based on quantum scattering

“…for bosons and fermions in accordance with (9). An integration (4) of both σ ′ (g, χ) and σ ′′ (g, χ) leads to the expressions…”

“…Nowadays, such potentials practically for all noble gases and their mixtures are available in the open literature, see e.g. [3][4][5][6][7][8][9][10]. Thus, the DSMC method based on AI potential [11] also becomes free from such adjustable parameters.…”

State-of-the-art ab initio potential energy curve for the xenon atom pair and related spectroscopic and thermophysical properties

“…In our previous work on the Ne-Ne, 8 Ar-Ar, 9 and Kr-Kr 12 systems, we used correlation-consistent (cc) basis sets [28][29][30][31][32][33][34][35][36][37] up to polarized-valence sextuple-zeta size (abbreviated here as V6Z) to reach the desired accuracy for the interaction energies. For krypton, we developed the V6Z basis set as part of our study.…”

“…For krypton, we developed the V6Z basis set as part of our study. 12 When we started the present work on the xenon atom pair, cc basis sets for xenon were only available for PP calculations. 38 However, employing a PP approach limits the accuracy that can be achieved for the potential energy curve.…”

“…Recently, highly accurate Kr-Kr potentials have been developed by Waldrop et al 11 and by our group. 12 The derived thermophysical property data for gaseous neon, 13 argon, 4,14,15 and krypton 11,12 are again of reference quality. However, their estimated uncertainties are considerably larger than those for helium because the potential energy curve of the four-electron He-He system can be determined much more accurately than the potential energy curves of the heavier rare gas pairs.…”