Novel high symmetrical body centered carbon allotropes: cubic C48 and tetragonal C32 are proposed with respective original “ana” and “ukc” topologies. Devised from crystal structure engineering, their ground state structures and energy derived physical properties were accurately derived from quantum mechanics calculations within the density functional theory DFT. Both allotropes made of distorted tetrahedral C4 arrangements were found dense with ρ > 3 g/cm3 that remains lower than diamond density: ρ = 3.55 g/cm3. With cohesive albeit metastable ground state structures versus diamond, both allotropes show stability from the mechanical (elastic properties), dynamic (phonons band structures), as well as thermodynamic properties that show relationship with diamond’s experimental CV = f(T) discrete results. Vickers hardness magnitudes HV(C48) = 47 GPa and HV(C32) = 59 GPa indicate super-hard materials. The electronic band structures range from large direct band gap ∼5 eV for C48 to indirect band gap ~2.5 eV of semi-conducting-like C32. Such findings of original allotropes with targeted physical properties are bound to enrich the field of research on carbon allotropes especially highly symmetrical ones.
Samir F. Matar (Sun,) studied this question.