Due to the complex potential energy surfaces of molecules on surfaces, it is desirable to consider all nuclear degrees of freedom. As this can be practically achieved using frictional Langevin dynamics with stochastic forces, most of the recent studies use this approach. Historically, due to the associated computational cost, still, only a few selected degrees of freedom were used. For the system of H/Ru(0001) Luntz et al. used a three-dimensional model, and later Füchsel et al. extended it to six dimensions (all degrees of freedom of two hydrogen atoms at a rigid surface). These studies used analytical potentials with parameters fitted to density functional theory (DFT) calculations. It is not easy to extend such analytical potentials to more than one molecule. Therefore, Juaristi et al. used directly DFT forces in Langevin dynamics, the so-called ab-initio molecular dynamics with electronic friction (AIMDEF) method that was later used to study different photo-induced reactions. This method allows studying more than two adsorbate atoms per unit cell with full dimensionality at the expense of orders of magnitude larger computational cost that severely limits statistical sampling. Specifically, in ref 17 the laser-induced desorption of hydrogen molecules from a (4×4) unit cell with 16 H (D) atoms was studied for a handful of selected H/D isotope ratios, at a single laser fluence and over a limited propagation time of 800 fs. In the present paper, we wish to go substantially beyond these limits in system size, H/D ratios, laser fluences, and propagation times to allow for a more systematic study.