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

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.