The stated structure shown in Fig. is a cubic fluorite-like one with face centered Si substructure, and C and N atoms occupying the fluorite F8 cube corners. Later, Chen et al. identified crystalline and amorphous SiCN in the process of thin films growth by microwave CVD; but no crystal structure was reported. The conducted nano-indentation study revealed a hardness value of 30 GPa for the crystalline phase and 22 GPa for the amorphous phase, therefore, the authors' claim that SiCN is a hard material rivaling cubic BN is unjustified. In 1997, Riedel et al. claimed the first ternary crystalline solid of the Si 2 C 2 N 4 stoichiometry built of SiN 4 tetrahedra (blue, Fig. ) interconnected via carbon atoms, thus leading to N 3 SiN--C--NSiN 3 -like chains of tetrahedra along vertical c-axis, corner sharing along horizontal x-y planes. This feature is also characteristic of the novel SiCN proposed herein except for a mixed N-C coordination polyhedron for Si.