Intermolecular potential energy surface and thermophysical properties of ethylene oxide

Abstract

A six-dimensional potential energy hypersurface (PES) for two interacting rigid ethylene oxide (C2H4O) molecules was determined from high-level quantum-chemical ab initio calculations. The counterpoise-corrected supermolecular approach at the MP2 and CCSD(T) levels of theory was utilized to determine interaction energies for 10178 configurations of two molecules. An analytical site-site potential function with 19 sites per ethylene oxide molecule was fitted to the interaction energies and fine tuned to agree with data for the second acoustic virial coefficient from accurate speed of sound measurements. The PES was validated by computing the second virial coefficient, shear viscosity, and thermal conductivity. The values of these properties are substantiated by the best experimental data as they tend to fall within the uncertainty intervals and also obey the experimental temperature functions, except for viscosity, where experimental data are insufficient. Due to the lack of reliable data, especially for the transport properties, our calculated values are currently the most accurate estimates for these properties of ethylene oxide.

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 expressions for the CH 4 -H 2 S and H 2 S-CO 2 molecule pairs are similar in structure; the expression for the rotational contribution of an asymmetric top (H 2 S) can be found, for example, in reference [6].…”

“…Such calculations have been performed for a number of simple gases, such as methane [9,10], carbon dioxide [5], hydrogen sulfide [4,11], water vapor [12,13], or ethylene oxide [6], yielding transport property values with an uncertainty commensurate with the best experimental measurements over wide temperature ranges. We have recently extended the calculations to binary mixtures and have reported values for three traditional transport properties (viscosity, thermal conductivity, binary diffusion coefficient) and for the cross second virial coefficient of (CH 4 + N 2 ) mixtures [8,14].…”

“…Transport properties in the dilute gas limit have been determined by means of the classical trajectory approach in conjunction with the kinetic theory of molecular gases [8,14,[24][25][26]. The accuracy and usefulness of this approach has been demonstrated for several pure molecular gases and gas mixtures, see, for example, references [5][6][7][8][12][13][14]. The calculation of all thermophysical properties presented in this work was performed in the temperature range from (150 to 1200) K.…”

“…The macroscopic properties of a dilute gas are governed by binary molecular interactions, and the recent computational advances in the field have allowed us not only to accurately determine the intermolecular potential energy surfaces (PESs) using quantum-chemical ab initio methods [3][4][5][6], but also to calculate the transport properties by making use of a rigorous molecular description [7,8]. Such calculations have been performed for a number of simple gases, such as methane [9,10], carbon dioxide [5], hydrogen sulfide [4,11], water vapor [12,13], or ethylene oxide [6], yielding transport property values with an uncertainty commensurate with the best experimental measurements over wide temperature ranges.…”

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

“…For small molecules, such calculations are nowadays routinely carried out, and accurate pair potentials exist for, among others, methane, 2 water, 3 hydrogen sulfide, 4 hydrogen, 5 nitrogen, 6 carbon dioxide, 7 and ethylene oxide. 8 Thermophysical properties have also been calculated for a number of these PESs. 2,4,[6][7][8][9][10][11] In this work, we extend our recent studies of pure gases 2,4,[6][7][8][9][10][11] to binary CH 4 -N 2 mixtures.…”