ABSTRACTThe synthesis of amorphous diamond thin films has been studied previously by classical molecular dynamics computer simulations utilising Stillinger Weber potentials, reparameterised to describe bonding in carbon. The simulations provided insight into the surface processes occuring during thin film growth and showed the role of stress and an energy window in promoting amorphous diamond formation from carbon ion beams. However, more realistic simulations require a full treatment of quantum effects to describe adequately chemical bonding and electronic properties. Local Density Functional theories and the Car-Parrinello molecular dynamics algorithm have proved to be successful and offer a route to first-principles materials design. We are using these techniques to investigate bonding and structure in small carbon clusters and to study doping of diamond required to fabricate electronic devices. Results are presented for a novel, three dimensional, neutral carbon-11 cluster which was studied by ab initio molecular dynamics simulations confirming that, while the 3D structure is stable, the ring is the lower energy structure. However, the 3D structure deforms rapidly to a more open structure of the same topology which is dynamically stable during simulated annealing up to 2000K. Higher quality calculations indicate that new, lower symmetry bonding arrangements form also. Attempts to enclose lithium or boron atoms within the Cl 1 cage caused heating and ultimate rupture into smaller fragments.
