Modelling of stress-induced diamond nucleation

PM3 semi-empirical calculations have been used to model the primary diamond nucleation in the graphite-like initial carbon layer usually produced on substrates other than diamond. The effect of quenched-in density increase was simulated by compressing the graphitic environment (represented by a small graphite cluster with cyclic boundary conditions) of a carbon atom with an additional methyl group in its vicinity. The critical (linear) compression for the “sp 2 → sp 3 phase transformation” of the fourfold coordinated carbon was estimated to be 3%.