The first criteria for assessing the relative stabilities are the atom-averaged cohesive energies provided in Table for the three title carbon allotropes as well as for diamond. The calculations were initiated starting from structure propositions in literature. However, the paper on 'glitter' C 6 by Bucknam and Hoffmann proposed the tetragonal space group P4 2 /mmc N°131 without providing lattice constants or atomic positions. Starting from the crystal data of silicon dicarbide belonging to the same space group with replacing carbon occupying the tetrahedral site (C1 in Fig. ) we arrived at the structure described in Table . This also stands for 'isoglitter' C 8 announced in Ammm space group whereas the accurate geometry optimizations led to a primitive mode orthorhombic space group Pmmm; the crystal data are given in Table and the crystal structure is depicted in Fig. . Lastly the calculated crystal data for C 8 are found in agreement with the formerly published structure . The presence of arrays of tetrahedra separated by C2-C2 pairs (Fig. ) similarly to 'glitter' and 'isoglitter' allows us to propose labeling this octacarbon as 'metaglitter'. The calculated crystal parameters are provided in Table .