Ab initio values of the thermophysical properties of helium as standards

Abstract

Recent quantum mechanical calculations of the interaction energy of pairs of helium atoms are accurate and some include reliable estimates of their uncertainty. We combined these ab initio results with earlier published results to obtain a helium-helium interatomic potential that includes relativistic retardation effects over all ranges of interaction. From this potential, we calculated the thermophysical properties of helium, i.e., the second virial coefficients, the dilute-gas viscosities, and the dilute-gas thermal conductivities of 3He, 4He, and their equimolar mixture from 1 K to 104 K. We also calculated the diffusion and thermal diffusion coefficients of mixtures of 3He and 4He. For the pure fluids, the uncertainties of the calculated values are dominated by the uncertainties of the potential; for the mixtures, the uncertainties of the transport properties also include contributions from approximations in the transport theory. In all cases, the uncertainties are smaller than the corresponding experimental uncertainties; therefore, we recommend the ab initio results be used as standards for calibrating instruments relying on these thermophysical properties. We present the calculated thermophysical properties in easy-to-use tabular form.

Microscale rarefied gas dynamics and surface interactions for EUVL and MEMS applications.

“…The viscosity and conductivity values of the two groups agree to within 0.20% and 0.12%, respectively, which is within the stated uncertainty of Bich et al (1990). The tabulated values for helium reported by Hurly and Moldover (2000) are also in excellent agreement (within 0.15%) with the Bich et al values.…”

“…These potential-based theoretical values are found to agree with the most reliable experimental data to within reported experimental accuracies (Hurly and Moldover, 2000;Aziz et al, 1995;Bich et al, 1990). Bich et al (1990) provide tables of the viscosity and thermal conductivity of the monatomic gases based on kinetic-theory (Chapman-Enskog) calculations of the transport properties using accurate HFD-B type interatomic potentials.…”

“…For this purpose, they report values at 298.15 K (25°C) of K = 154.81 ± 0.08 mW/(m⋅K) and η = 19.800 ± 0.010 µPa⋅s. More recently, Hurly and Moldover (2000) also claim that the uncertainties in their tabulated, ab initio values of the thermophysical properties of helium are smaller than the corresponding experimental uncertainties.…”

“…For monatomic gases, several authors (Hurly and Moldover, 2000;Aziz et al, 1995;Bich et al, 1990) have suggested that the most accurate estimates of the transport properties of monatomic gases can be obtained based on kinetic-theory calculations using accurate ab initio interatomic potentials. These potential-based theoretical values are found to agree with the most reliable experimental data to within reported experimental accuracies (Hurly and Moldover, 2000;Aziz et al, 1995;Bich et al, 1990).…”

Dipole and quadrupole polarizabilities and shielding factors of beryllium from exponentially correlated Gaussian functions

“…Formally, the polarizability is defined as a second derivative of the perturbation-dependent energy ͓9͔ ␣ ϭϪ2E (2) .…”