Ab-initio calculations of the electronic structure and cohesive properties of the orthorhombic oxynitrides x₂n₂o (x = c, si, ge)

The full-potential LMTO method was used for the investigation of the electronic structure and chemical bonding of the silicon, germanium and hypothetical carbon oxynitrides. The isovalent substitution of Si by C allows to compare the role of Si and C in the processes of chemical bonding and cohesive properties. It was shown that doping by carbon may lead to stronger covalent bonding and therefore the new ceramic materials based on the Si-C-Al-O-N system can have improved mechanical characteristics.