Ab initio virial equation of state for argon using a new nonadditive three-body potential

Abstract

An ab initio nonadditive three-body potential for argon has been developed using quantum-chemical calculations at the CCSD(T) and CCSDT levels of theory. Applying this potential together with a recent ab initio pair potential from the literature, the third and fourth to seventh pressure virial coefficients of argon were computed by standard numerical integration and the Mayer-sampling Monte Carlo method, respectively, for a wide temperature range. All calculated virial coefficients were fitted separately as polynomials in temperature. The results for the third virial coefficient agree with values evaluated directly from experimental data and with those computed for other nonadditive three-body potentials. We also redetermined the second and third virial coefficients from the best experimental pρT data utilizing the computed higher virial coefficients as constraints. Thus, a significantly closer agreement of the calculated third virial coefficients with the experimental data was achieved. For different orders of the virial expansion, pρT data have been calculated and compared with results from high quality measurements in the gaseous and supercritical region. The theoretically predicted pressures are within the very small experimental errors of ±0.02% for p ≤ 12 MPa in the supercritical region near room temperature, whereas for subcritical temperatures the deviations increase up to +0.3%. The computed pressure at the critical density and temperature is about 1.3% below the experimental value. At pressures between 200 MPa and 1000 MPa and at 373 K, the calculated values deviate by 1% to 9% from the experimental results.

Communication: Ab initio Joule–Thomson inversion data for argon

“…Here we show that a seventh-order ab initio virial EOS for argon [20][21][22] gives rise to (high-temperature) JT inversion data in excellent agreement with the reference data set 5 up to the maximum inversion pressure. We also argue that the obtained JT inversion curves provide some insight into the range of applicability and high-density behavior of the truncated virial EOS.…”

“…Jäger et al have reported smooth temperaturedependencies of B 2 to B 7 in terms of fits (of Laurent polynomials in √ T ) to discrete B n data computed from ab initio two-body 21,22 and non-additive three-body potentials. 22 We use these fits to compute the JT inversion curve by solving…”

Cross second virial coefficients and dilute gas transport properties of the (CH 4 + CO 2 ), (CH 4 + H 2 S), and (H 2 S + CO 2 ) systems from accurate intermolecular potential energy surfaces

“…The hard-sphere fluid with a sphere diameter of 0.45 nm was used as reference system. Results for all temperatures were obtained simultaneously by performing multi-temperature simulations [22,37] with a sampling temperature of 150 K and 2 × 10 10 trial moves. For each trial move, one of the molecules was displaced and rotated.…”

Intermolecular potential energy surface and thermophysical properties of the CH4–N2 system

“…Results for all temperatures were obtained simultaneously by performing multitemperature simulations 6,23,44 with a sampling temperature of 70 K and 2 × 10 10 trial moves. For each MC trial move, one of the molecules was displaced and rotated.…”