Cosmic Silicate Surfaces Catalizing Prebiotic Reactions: Atomistic Modeling on the Polymerization of HCN

Hydrogen cyanide, HCN, is a fundamental building block in astro- and cosmochemical environments, known for its ability to form prebiotically relevant molecules such as nucleobases. Although its polymerization is inhibited under the cold, dilute conditions of the interstellar medium, the higher temperatures of more evolved rocky bodies, combined with the presence of mineral surfaces, can catalyze the reaction. In this study, we use atomistic simulations grounded on the density functional theory (DFT) to elucidate the complete tetramerization pathway of HCN to diaminomaleonitrile (DAMN) and diaminofumaronitrile (DAFN), catalyzed by the crystalline Mg₂SiO₄ forsterite (120) surface. Results demonstrate that the intrinsic acid-base properties of the surface facilitate chemical bond formation/cleavage needed for HCN oligomerization, lowering activation barriers by ∼120-220 kJ mol^-1 with respect to the gas-phase. Kinetic analyses reveal that the reactions are feasible at temperatures above 300 K, particularly under conditions present in warm, rocky bodies such as asteroids, meteorites, and planetary surfaces. The presence of water further accelerates key steps by assisting proton transfer processes. These findings support a model in which Mg-rich silicate minerals (abundant in the early Solar System) may have directly catalyzed the formation of complex organic molecules, which, in turn, are precursors of more complex biomolecules, thereby contributing to the essential chemical inventory for the emergence of life on early Earth and other primitive planets with propitious conditions.