Computing Binding Energies of Interstellar Molecules by Semiempirical Quantum Methods: Comparison Between DFT and GFN2 on Crystalline Ice

Abstract Interstellar Grains (IGs) spread in the Medium (ISM) host a multitude of chemical reactions that could lead to production interstellar Complex Organic Molecules (iCOMs), relevant context prebiotic chemistry. These IGs are composed silicate-based core covered by several layers amorphous water ice, known as grain mantle. from ISM gas-phase can be adsorbed at surfaces, diffuse and react give iCOMs ultimately desorbed back gas phase. Thus, study Binding Energy (BE) these molecules ice surface is important understand molecular composition its evolution time. In this paper, we propose use recently developed semiempirical quantum approach, named GFN-xTB, more precisely GFN2 method, compute BE species crystalline slab model. This method very cheap term computing power time was already showed previous work accurate with small clusters. To support our proposition, decided use, benchmark, recent published some us which model proton-ordered (P-ice) adopted predict BEs 21 ISM. The relatively good results obtained confirm choice adsorption processes occurring icy grains only notable exception for CO molecule, both structure badly predicted GFN2, real pity due relevance astrochemistry.