In this report the interaction between SiH2 molecules and a SiC-4H (0001) surface and SiCl2 molecules and a SiC-4H (0001) surface is investigated. This is done using a cluster model to represent the surface. First the clusters are investigated by calculating some properties to compare with experimental data to motivate the use of the cluster model. The band gap calculated by extrapolation for an infinitely large cluster is 3.75 eV which is fairly close to the experimental value of 3.2 eV. Adsorption studies are performed and the main conclusion is that the SiH2 molecule adsorbs more strongly on the surface then the SiCl2 molecule, adsorption energies are calculated to approximately 200 kJ mol-1 and 100 kJ mol-1 respectively. At the end a few migration studies are performed with the conclusion that SiCl2 more easily can diffuse on the surface compared to the SiH2 molecule. The respective activation energies for migration on the surface are 4 kJ mol-1 for SiCl2 and 87 kJ mol-1 for SiH2.