Template tet-C 3 and C-inserted system resulting into C 6 were submitted to unconstrained geometry optimization down to the ground state energies. The lattice parameters and energies are given in Table . The data obtained earlier for C Although E coh./at. =(C 6 )= -1.93 eV is smaller than E coh./at. =(C 5 )= -2.05 eV, it remains higher that the calculated magnitudes obtained for B 12 C 3 (E coh./at =-1.66eV) or C 3 (E coh./at = -1.55 eV), cited above. Consequently, it can be suggested that embedding tricarbon within a tetrahedral network (here C 3 ) is a major stabilizing factor, better than the insertion of C-C-C within a large cavity as rh-B 12 (-Boron) or as a standalone structure directly connecting C2-C1-C2 through terminal C2 carbon atoms .