The novel C 16 structure derived from tet-C 4 was submitted to full geometry optimization of the lattice parameters and the atomic positions to stress-free ground state. Subsequent symmetry analysis allowed assigning the crystal space group P-4m2, N° 115. The crystal data provided in Table show 6 different positions for carbon in this space group. There is a unique C-C distance amounting to d(C-C) = 1.547 Å identical to the diamond (cf. ref. ). The distribution of carbon into 1, 2 and 4 -fold Wyckoff positions is an interesting feature, allowing to consider possibilities of different sets of substitutions with loss of symmetry within the tetragonal space group P-4m2. Indeed, to obtain B 8 N 8 the substitutions of C1 -C4 by B and C5-C6 by N were performed, followed by fully unconstrained geometry optimization. The results in Table show no perturbation of the structure (P-4m2) while preserving the same Wyckoff positions. The structure shown with tetrahedral-like local coordinations of B and N is characterized by a unique d(B-N) = 1.561 Å.