Three-Body Nonadditive Potential for Argon with Estimated Uncertainties and Third Virial Coefficient

Abstract

The three-body nonadditive interaction energy between argon atoms was calculated at 300 geometries using coupled cluster methods up to single, double, triple, and noniterative quadruple excitations [CCSDT(Q)], and including the core correlation and relativistic effects. The uncertainty of the calculated energy was estimated at each geometry. The analytic function fitted to the energies is currently the most accurate three-body argon potential. Values of the third virial coefficient C(T) with full account of quantum effects were computed from 80 to 10000 K by a path-integral Monte Carlo method. The calculation made use of an existing high-quality pair potential [Patkowski, K.; Szalewicz, K. J. Chem. Phys. 2010, 133, 094304] and of the three-body potential derived in the present work. Uncertainties in the potential were propagated to estimate uncertainties in C(T). The results were compared with available experimental data, including some values of C(T) newly derived in this work from previously published high-accuracy density measurements. Our results are generally consistent with the available experimental data in the limited range of temperatures where data exist, but at many conditions, especially at higher temperatures, the uncertainties of our calculated values are smaller than the uncertainties of the experimental values.

Density-functional approach to the three-body dispersion interaction based on the exchange dipole moment

“…We use these data to optimize and test the three-body damping functions proposed here, along with other two data sets available in the literature: highly accurate nonadditive three-body interaction analytical potential fitted to FCI results for He 3 trimers 21 and to coupled-cluster results using single, double, triple, and noniterative quadruple excitations (CCSDT(Q)) for Ar 3 trimers. 12 In the latter two cases, we use the supplied routines in these references to calculate a series of symmetry unique He 3 and Ar 3 trimers. The geometries of this series are generated by even-spaced increments starting from the equilibrium bond lengths (5.6 bohrs for He 3 and 7.1 bohrs for Ar 3 ) and ending to 2.5 times longer lengths.…”

“…They proposed that the non-additive three-body dispersion component can be deduced by subtracting the Møller-Plesset perturbation theory (MP2) energy from the energy of the CCST(T). Accurate estimates of the three-body nonadditive interaction potential in He 3 and Ar 3 trimers have been recently reported as well by Szalewicz and Co., 12,20,21 based on fitting the terms of SAPT to the results of full configuration interaction (FCI) for He 3 and high-order coupled-cluster method for Ar 3 .…”

“…The preliminary assessment of this model is encouraging, especially concerning the C 9 values of a series of noble atom triplets that agree well with highly accurate values in the literature, including the recent XDM-based post-HF results of Otero-de-la-Roza and Johnson. 8 Based on the accurate estimate of C 9 with our method, we confirm the accuracy of the high-level theoretical estimate of the nonadditive three-body intermolecular dispersion interaction for a series of benzene trimers by Sherrill and Co. 9 For the unsettled question of damping for the nonadditive three-body dispersion, 8 we propose two new schemes and benchmark and optimize them against a combined set of data including the series of benzene trimers considered by Sherrill and Co., as well as a set of He 3 and Ar 3 trimers for which accurate fitted SAPT data have been reported by Szalewicz and Co. 12,21 Both schemes respond well to optimization and show comparable performance after the optimization, with Scheme A doing overall slightly better. Besides the data on molecular crystals and noble gas trimers, further improvement on the modeling of the nonadditive three-body interactions can be achieved by computing the third virial coefficients and comparing with theoretical and experimental values.…”

“…Besides the data on molecular crystals and noble gas trimers, further improvement on the modeling of the nonadditive three-body interactions can be achieved by computing the third virial coefficients and comparing with theoretical and experimental values. 8,9,12 …”

“…7,[10][11][12] Current DFT methods tend to overestimate the two-body dispersion interaction partly due to the omission of the three-body contribution that is often of the opposite sign. 7 The general formulas for the nonadditive threebody dispersion were derived long ago based on perturbation theory and dynamic polarizabilities, [13][14][15] but were not applied in DFT studies of VDW systems until recent years.…”