Silicon quantum dots have a multitude of potential uses within the biomedical and optoelectronic industries due to the outstanding optical properties they exhibit. However, they are susceptible to oxidation, which may have a significant impact on the yield and emission wavelength. These effects may be traced to the growth of a Si02 capping layer, or the inclusion of surface defects that yield optically active mid-gap states. Therefore the results of density functional calculations examining important oxidation processes for silicon quantum dots are presented within this thesis. The results have been obtained using the AIMPRO (Ab Initio Modelling PROgram) DFT code. First, a discussion is included concerning the thermodynamic and kinetic preferences for oxygen migration at the surface of a quantum dot, a key process in the growth of a Si02 layer, in particular examining the effects of local surface bonding and charging. Following on from this analysis, the progressive oxidation of a quantum dot through the formation of Si-O-Si bonds or the oxidation of surface SiH bonds has been examined to determine the most energetically favourable route for oxidation and the effect on the optical response of the system. Finally, the silanone surface defect (Si=O) has often been cited in the literature as a potential source of optical shifts upon exposure to an oxidising source. However the stability of this structure has only been analysed in a few idealised circumstances, and a more general and significantly extended study is included.