On the unusual behavior of nitride compounds
  This report presents consistent insight into the mechanism behind the unusual behavior of nitride compounds from the perspective of tetrahedron bond formation and its consequence on valence density of states. An extension of the recent bond-band-barrier (BBB) correlation mechanism for oxidation [Sun CQ, Prog Mater Sci 2003;48:521-685] to the electronic process of nitridation has led to the essentiality of sp-orbital hybridization for a nitrogen atom upon interacting with atoms in solid phase of arbitrary less-electronegative element. In the process of nitridation, a nitrogen atom forms a quasi-tetrahedron with surrounding host atoms through bonding and nonbonding interaction associated with production of electronic holes and antibonding dipoles, which add corresponding density of states to the valence band of the host. It is suggested that the valance alteration of the system takes the responsibility for the blue shift in photoluminescence, lowered work function for cold cathode field emission, corrosion and wear resistant, high elasticity, and magnetic modulation as well. 
W. T. Zheng and Chang Q. Sun