Modelling of Si-B-N ceramics

We present results of computer simulations of amorphous Si3B3N7 ceramics. The computed pair correlation functions are in agreement with the experimental results. Regarding the structural properties of the B-N, Si-N and N-Si/B coordination spheres, our results are in full agreement with experimental data. We confirm that silicon is tetrahedrally coordinated by nitrogen, and boron is trigonally planar coordinated by nitrogen. Furthermore we find that the coordination of nitrogen by the cations is also trigonally planar. Additionally our results suggest that a significant structural property of these materials is a heterogenity on a lengthscale of about 0.5nm. The simulation of relaxation and annealing processes of this new substance indicate the existence of rather stable BN3 building units, while the SiN4 building units are comparatively malleable.