Abstract
Two important aspects of CVD diamond growth are considered in this work; graphitisation of diamond at the intersection of twin boundaries with {111} surfaces, and surface mobility of hydrogen and other species. The results of our local spin-density functional based calculations show that twin boundaries can induce graphitisation in their vicinity if there is no surface hydrogen to stabilise the diamond structure. We also show how hydrogen may be mobile on certain diamond surfaces by a dangling bond diffusion mechanism and conclude that this may play a role in the CVD growth process.