COMPUTER-MODEL OF TETRAHEDRAL AMORPHOUS DIAMOND

We computer generate a model of amorphous diamond using the Wooten-Wea ire method, with fourfold coordination everywhere. We investigate two models: one where four-membered rings are allowed and the other where the four-membered rings are forbidden; each model consisting of 4096 a toms. Starting from the perfect diamond crystalline structure, we firs t randomize the structure by introducing disorder through random bond switches at a sufficiently high temperature. Subsequently, the tempera ture is reduced in stages, and the topological and geometrical relaxat ion of the structure takes place using the Keating potential. After a long annealing process, a random network of comparatively low energy i s obtained. We calculate the pair distribution function, mean bond ang le, rms angular deviation, rms bond length, rms bond-length deviation, and ring statistics for the final relaxed structures. We minimize the total strain energy by adjusting the density of the sample. We compar e our results with similar computer-generated models for amorphous sil icon, and with experimental measurement of the structure factor for (p redominantly tetrahedral) amorphous carbon.