argon; ab initio; rare gas trimer; interations

Three-body contributions to the interaction energy of Ar3 have been calculated using the HF ? CCSD(T) method and multiply augmented basis sets due to Dunning and co-workers [1]. The calculations have been performed using the MOLPRO 2002 suite of quantum-chemistry programs. The basis set superposition error has been treated through the counterpoise correction by Boys and Bernardi [2], the convergence to the complete basis set has been analyzed, and both the triple-excitation and core-electron contributions to the three-body energy of Ar3 have been assessed. A complete nonaditive potential has been fitted to 330 computed points and compared with other points.