  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.
