New Metallic Carbon Crystal

Abstract

Recently, mathematical analysis clarified that $s{p}^2$ hybridized carbon should have a three-dimensional crystal structure ($K_4$) which can be regarded as a twin of the $s{p}^3$ diamond crystal. In this study, various physical properties of the $K_4$ carbon crystal, especially for the electronic properties, were evaluated by first principles calculations. Although the $K_4$ crystal is in a metastable state, a possible pressure induced structural phase transition from graphite to $K_4$ was suggested. Twisted $\pi$ states across the Fermi level result in metallic properties in a new carbon crystal.