Third virial coefficient of argon

The classical third virial coefficient of argon has been computed for tempe ratures between 113.15 K and 1223.15 K using an ab initio three-body potent ial. The results agree with the virial coefficients extracted directly from experimental data to within about 5% for temperatures between 220 K and 42 0 K, theory almost touching the experimental error bars. For lower temperat ures the discrepancies become larger, but results from different experiment s are also significantly apart. Our calculated values agreed very well with those of Dymond and Alder [J. Chem. Phys. 54, 3472 (1971)] determined by f itting experimental data with theoretical constraints. The equation of stat e obtained using the computed second and third virial coefficients reproduc ed experimental PV data over a wide range of pressure. (C) 1999 American In stitute of Physics.