  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.
