Modeling H$_2$-Surface Interactions on Interstellar Dust Grains: A Classical Molecular Dynamics Study*

A classical Molecular Dynamics (MD) method is employed to model hydrogen molecules interacting with the surface of amorphous ice and to calculate the sticking coefficient as a function of various system parameters. This study, combining molecular physics and surface science, is part of a larger program of research to provide theoretical input for models of dust-grain-mediated physico-chemical processes in the interstellar medium. Many dust-grain species are thought to be clad in amorphous ice, which motivates the choice of substrate for this study. Our method simulates the various dynamical processes associated with H$_2$-ice scattering events, including collision, sticking, diffusion, and ejection. Variables such as angle of incidence, molecular rotational state, substrate temperature ($T_D$), and H$_2$ temperature ($T_{\rm H_2}$) are monitored and allowed to vary. In this talk, we will present our results for the H$_2$-ice sticking coefficient as a function of $T_D$ and $T_{\rm H_2}$.