Thermophysical properties of argon gas from improved two-body interaction potential
Jakub Lang, Michał Przybytek, Michał Lesiuk
Abstract
Ab initio interaction potential for the electronic ground state of the argon dimer has been developed. The potential uses previously calculated accurate Born-Oppenheimer interaction energies while significantly improving the description of relativistic effects by including the two-electron Darwin and orbit-orbit corrections. Moreover, leading-order quantum electrodynamics corrections to the potential are calculated, and long-range retardation of the electromagnetic interactions is taken into account. Spectroscopic properties of the argon dimer are reported, such as the bond dissociation energy, positions of rovibrational levels, and rotational and centrifugal-distortion constants. Our potential supports eight rotationless vibrational states, and the existence of a ninth level can neither be confirmed nor ruled out at the current accuracy level. Finally, thermophysical properties of the argon gas, including pressure and acoustic virial coefficients, as well as transport properties---viscosity and thermal conductivity---are evaluated using the developed potential. For the virial coefficients, the obtained ab initio values are somewhat less accurate than the most recent experimental results. However, the opposite is true for the transport properties, where the theoretical results calculated in this work have significantly smaller uncertainties than the data derived from measurements.