Later, a silicon dicarbide Si 2 C 4 (Fig. ) was theoretically proposed based on tetragonal C 6 , by replacing tetrahedral C1 by Si leading to SiC4 tetrahedra connected through the two C2 characterizing the structure . With the objective of identifying SiCN ternary compound in view of the inefficiency of the cubic setup proposed earlier , or of cyanide like SiCN, we come up with the equiatomic stoichiometry through replacing one of the two trigonal carbons (C2) by N leading to SiC2N2 tetrahedra. The ad hoc structure submitted to unconstrained geometry relaxation led to a lowering of the tetragonal space group symmetry to P4 2 mc N°105. The ground state equiatomic structure is depicted in Fig. . To the best of our knowledge, no propositions have been made of equiatomic SiCN structure or existence beside the 1965 paper .