Astrochemical reaction network including deuterated molecules

<sec><p indent="0mm">Astrochemical reaction networks are one of the tools to study the synthesis and evolution of interstellar molecules. By simulating astrochemical reaction networks under physical conditions that pertain to specific astronomical sources, the abundance of interstellar molecules and their temporal evolution can be predicted. This helps to understand the fundamental laws of interstellar molecular evolution. Deuterated molecules are an important component of the interstellar medium. The detection and study of deuterated molecules provide critical observational evidence and theoretical constraints for the development of astrochemical reaction networks. </sec><sec> In recent years, as astrochemical research advanced, an increasing number of deuterated molecules have been discovered in interstellar space, sparking greater interest in the formation and evolution of these molecules in the universe. These discoveries have driven further development of the chemical reaction networks involving deuterated molecules, enabling a better understanding of the synthesis, transformation, and evolution of deuterated molecules in various interstellar environments. The formation of deuterated molecules is closely linked to low-temperature and high-density physical conditions. In such environments, the frequency of molecular collisions increases, and chemical reactions occur more frequently and efficiently, providing the necessary impetus for deuteration reactions. The realization of deuteration is a complex process, involving multiple reaction pathways, including the incorporation and substitution of deuterium atoms. Deuteration reactions are not limited to gas-phase reactions; they also include surface reactions on dust grains. On the surfaces of interstellar dust, molecular processes such as molecular adsorption, synthesis, and desorption significantly influence the efficiency of deuteration reactions. To better understand the formation mechanisms of deuterated molecules in different interstellar environments, astrochemical reaction networks must fully account for these complex reaction processes. </sec><sec> The KIDA database, one of the most widely used gas-phase chemical reaction networks, already includes a significant number of reactions involving deuterated molecules. The chemical reaction networks for deuterated molecules in this database mainly focus on gas-phase reactions, so they lack a comprehensive description of surface reactions on dust grains. Dust grains play an important role in the interstellar medium, acting not only as catalysts for molecular reactions but also as sites where processes such as adsorption, desorption, and surface chemical reactions can take place. Surface reactions on dust are crucial for the synthesis of deuterated molecules, making it essential to improve the reaction networks in this area. To address this gap, we have extended the KIDA gas-phase deuteration reaction network by incorporating key surface reactions that occur on dust grains. These reactions mainly include molecular adsorption, desorption, synthesis, and decomposition on the surfaces of dust particles. The updated reaction network allows for a more comprehensive simulation of the evolution of deuterated molecules in various interstellar environments, providing a more accurate and complete theoretical foundation for future astrochemical simulations. </sec><sec> Under the classical physical conditions of cold molecular clouds, we used this extended network to simulate the synthesis of deuterated molecules. Preliminary simulation results indicate that the newly expanded chemical reaction network involving deuterated molecules can be used for subsequent modeling studies of deuterated species. </sec>