First principles study on the new sp3 bonded metallic carbon crystal

We report the results of the first principles studies of the electronic structure of simple cubic phase of carbon crystal, which exhibits metallic behavior. The charge density analysis shows that simple cubic phase of carbon is sp3 bonded system and confirms the promotion of one electron from 2s to 2p orbital due to the sp3 hybridization. The six orthogonal bonds made up of p orbitals protrude from the sphere shaped s orbital charge distribution. The bonds between the atoms are semi-covalent and weak due to the insufficient valence electrons. This reduction in covalency contrast to diamond induces the metallic nature in the simple cubic carbon. From the total energy calculation, the possibility of pressure induced phase transition from diamond to simple cubic carbon is predicted.