Many relevant chemical processes bringing simple molecules like H2, CO, NH3, CH4 and H2O to form iCOMs (interstellar Complex Organic Molecules) occur at the surface of interstellar dust grains, solid particles with fraction of a micron size being part of molecular clouds. In diffuse clouds the grains are mainly composed of olivine silicates or carbonaceous material (cores), while in dense clouds the core is covered by amorphous solid water (AWS) formed by reacting H and O atoms at the core surface. The accretion process results in a water multilayer (mantle) which adsorbs other simple molecules and radicals that may eventually react due to catalytic role played by the AWS to give iCOMs.
The thesis project aims to model, by quantum mechanical methods, the structure of the amorphous olivine core grains and to study the formation of water at their defective surface. The building up of the AWS mantle will also be simulated to provide realistic models of the grain mantle. Adsorption of simple molecules and radicals of astrochemical interest at the AWS surface will be simulated to provide quantum mechanical accurate binding energy for numerical astrochemical models and for comparison with the laboratory experience of ESR10.
The mantle models will be provided to ESR9 to simulate chemical reactive steps of neutral and radical species. The infrared spectral features of the adsorbates will be computed to be compared with future JWST observations of ices.
The thesis is part of the ACO network, whose ultimate goal is to reconstruct the early history of the Solar System by comparing presently forming solar-type planetary systems with its small bodies. The comparison will be based on the most advanced astrochemical knowledge, which will be developed by the interdisciplinary ACO team.