Calculation of the Transport and Relaxation Properties of the Ar···HCl van der Waals Complex Using a New Potential Energy Surface: Comparison of the Classical and Full Quantum Mechanical Kinetic Theory Results with Molecular Dynamics Simulations

Abstract

The intermolecular potential energy surface (PES) of the Ar•••HCl complex was calculated at the RCCSD(T)/aug-cc-pvQz-BF level of theory. The obtained potential was expanded in terms of Legendre polynomials and fitted to a mathematical model. The fitting results are highly correlated with the ab initio PES data with SD = 5.9 × 10 −3 cm −1 and average absolute deviation (AAD) = 4.0 × 10 −6 cm −1 . The interaction second virial coefficients (B 12 ) in the temperature range of 190−480 K were calculated by considering classical and first quantum corrections and compared with the available experimental data. A reasonable agreement with the experimental and calculated B 12 was obtained. The PES was also used to obtain the rovibrational energy levels, and the spectroscopic rovibrational constants were obtained. It was found that the D 0 values differ ∼2.25 cm −1 from the experimental values of the ground rovibrational state. Furthermore, the obtained potential was used to calculate the transport and relaxation properties using full quantum close-coupling (CC) formalism and the classical kinetic theory methods based on the Mason−Monchik approximation (MMA). It was found that the deviation between MMA and CC calculations is increased with increasing the temperature due to the higher influence of the rotational degrees of freedom on the transport properties. Also, the contribution of the inelastic (off-diagonal) transitions for diffusion coefficient is higher than the viscosity. Furthermore, the classical molecular dynamics simulations were performed using LJ(12,6) and Vashishta models, to calculate the interaction diffusion and viscosity coefficients, and compared with the results of the full quantum CC calculations. The obtained results confirm that the Vashishta model is better fitted to the ab initio potentials and is more accurate than LJ(12,6) in calculation of the diffusion coefficients.

PES and transport properties of the He⋯HBr complex from kinetic theory and molecular dynamics simulations

“…In summary, the scattering matrices were calculated from the close-coupling (CC) method in a wide range of energies using the PES, and energy dependent SBE cross sections then was calculated for each energy, and integrated over the considered energies in a desired temperature to obtain temperature dependent cross sections. 30,31,41…”

“…, vdW forces) or hydrogen bonds. 29 Our group has also recently reported the PESs of Ar⋯HCl 30 and He⋯CO 2 31 vdW complexes, and the transport and relaxation properties were computed by implementing different classical and quantum mechanical approaches.…”

“…Also, we could not find any experimental or calculated values for the transport properties of the He⋯HBr vdW complex in the literature; so, the obtained PES was also used to calculate the viscosity and diffusion coefficients in a wide range of temperatures using the methods developed in our previous works. 30,31…”

Quantum mechanical and classical calculation of the transport and relaxation properties of He⋯CO2 complex using a new PES

“…Recently, the PES of Ar⋯HCl at RCCSD(T)/aug-cc-pVQz-BF level of theory was calculated by our group, and the obtained PES was used to calculate the transport and relaxation properties of the Ar⋯HCl vdW complex. 43…”

“…Recently, the PES of ArÁ Á ÁHCl at RCCSD(T)/aug-cc-pVQz-BF level of theory was calculated by our group, and the obtained PES was used to calculate the transport and relaxation properties of the ArÁ Á ÁHCl vdW complex. 43 In this study, the super-molecular RCCSD(T) method using an aug-cc-pVQz-BF basis set was implemented to calculate the PES of HeÁ Á ÁCO 2 complex. The counterpoise correction method of Boys and Bernardi 44 was used to correct basis set superposition error (BSSE).…”