Lastly, the other alkaline cyanides ACN (A = Li, K, Cs) characterized solely by A-N connections were also considered in the preliminary calculations but all led to lower cohesive energies versus square-planar NaCN-type SiCN (Fig. ). Such results can be chemically expected since ACN cyanides are A+ CN-, i.e. "ionic", whereas SiCN cannot be a cyanide but rather a carbonitride, whence the interest in proposing a stable phase with tetrahedral SiC2N2 motifs.