Comer nitrides

In the face-centred cubic structure there are four atoms per unit cell, 8x1/8 cube comers and 6x1/2 face centres. There are also four octahedral holes, one body centre and 12 x 1/4 on each cube edge. When all of the holes are filled the overall composition is thus 1 1, metal to interstitial. In the same metal structure there are eight cube comers where tetrahedral sites occur at the 1/4, 1/4, 1/4 positions. When these are all filled there is a 1 2 metal to interstititial ratio. The transition metals can therefore form monocarbides, nitrides and oxides with the octahedrally coordinated interstitial atoms, and dihydrides with the tetrahedral coordination of the hydrogen atoms. 

Interaction of I2 with concentrated NH3 solution at room temperature gives black crystals of (NI3-NH3) , n = 1, 3, 5, that are explosive when dry. The crystals have zigzag chains of NI4 tetrahedra sharing comers with NH3 molecules linking the chains together. Pure NI3 has been made as red-black explosive, volatile crystals by interaction of boron nitride with IF in CFC13.73... 

Nitrides can be obtained by decomposition of the azides, but thermolysis of the pentahalides with ammonium salts appears more general. Recent synthetic pathways involve the cleavage of N2 or decarboxylation of a Nb isocyanate." The solid-state characterization of the [M2NXio] anions shows a linear symmetrical M=N=M bridge. Neutral halide nitrides are polymeric. Heterometallic nitrides based on a comer-shared double cube NbTieNg core (27) have been described (equation 14). ... 

The nitride Fe4N has a face-centred cubic lattice of iron atoms with a nitrogen atom at the body centre. Each comer FeA atom has 12 Fes neighbours at... 

Only a few ternary silicon nitrides have been prepared in a pure form and characterized. The isotypic compounds MSiN2 (M = Be, Mg, Mn, Ca, Zn), with the same valence electron concentration of 4, can be considered as ternary substitution variants of AlN [247]. These compounds contain three-dimensional (3-D) infinite network structures, with SiN4 tetrahedra linked through all four vertices by comer-sharing, which forms condensed [SieNe] twelve-membered rings in MgSiN2 [248]. 

At the comer of the Si—Al—O—N phase diagram closest to aluminum nitride (see Figure 5.1), there occur a series of phases, characterized by extended ranges of... 

Two modifications of crystalline boron nitride are known. In the cubic modification, each B atom is surrounded by four N atoms at the comers of a tetrahedron and vice versa. The mean bond energy calculated from the energy of atomization is 321 kJ mol and about 2.5 times larger than the N-B bond dissociation energy of the amine borane complex. 

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