The tangential momentum accommodation coefficient (TMAC) of argon atoms on a Pt(111) surface has been investigated using a multi-scale computational approach in order to emphasize the effect of the Pt-Ar pairwise potential on this parameter. For the different Pt-Ar pairwise potentials available in the literature, the TMAC has been determined by Molecular Dynamics simulations from the difference of the incident and reflected velocities of projected Ar atoms on the atomistic Pt surface. Temperature and incident angle dependencies of this parameter are also explored. A new Pt-Ar potential has also been calculated using periodic density functional theory computations. The resulting potential successfully reproduced the available experimental data and is compared with the previous empirical potentials. The TMAC deduced from our pairwise potential is 0.42 at T = 300 K.