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In this Thesis, computational models for carbonaceous dust grains were examined and compared to known experimental data. Different formation routes of molecules, important to the astrochemical evolution of the universe, have been investigated and their relative energies were analysed with respect to the harsh conditions in interstellar dark clouds of extremely low pressure (10‐17 bar) and temperature (10 – 20 K). Dust grains are present in the universe, and evidence shows they are siliceous or carbonaceous, possible with an icy mantle surrounding the core. In this research, only carbonaceous surfaces were examined. Two models were used to represent polycyclic, aromatic carbonaceous surfaces: coronene, C24H12, representing a relatively small hydrocarbon, and graphene – a single graphite sheet – which represents an extended carbonaceous surface. The main aims of this Thesis were to examine the validity of computationally modelled astrochemical reactions and to investigate the catalytic effect of dust grain surfaces on these reactions. Several formation reactions were examined, including water, methanol and carbonyl sulfide formation. The abundance of these molecules in dark molecular clouds cannot be explained by solely considering gas phase type reactions, and the influence that the carbonaceous surfaces have on these reactions was investigated in order to examine any catalytic effect that they may have. |
