The cluster models were created using Avogadro based off the models given in Reference 23. Dangling silicon bonds at the surface edges were terminated by OH species. All calculations were performed using the Gaussian 09 software. Geometry optimisations and frequency calculations were performed on the model structures prior to the calculation of NMR parameters. Note: no imaginary values were observed in the frequency calculations, and as such the structures were determined to be at the true minima. All calculations were carried out at the CAM-B3LYP/pcS-2 level of theory.