A New Carbon Allotrope With C28 Cage: T-C-64

A new tetragonal carbon allotrope (named T-C-64) is predicted by swarm structural searches combined with first principles calculation. It contains 64 carbon atoms in a Tetragonal unit cell with I4(1)/amd symmetry and exhibits distinct topologies including C28 cages. This new carbon phase has an sp(2)-sp(3) network with calculated hardness of 68.2 GPa. In order to examine the stability of T-C-64 under ambient pressure, we calculated the properties of elastic constant and phonon spectrum. In addition, by calculating the electronic properties of the crystal, it is concluded that T-C-64 is an indirect band gap semiconductor with a band gap of 2.23 eV.