| Abstract | In this Comment, we show that the investigation of Itoh et al. [1] on the electronic properties of a new cubic structure of carbon, the K4 crystal, is incomplete. This K4 structure was derived originally from the enumeration of 3D connected nets of atoms, and subsequently rediscovered from graph theory (see Ref. [2] and references cited therein). From first-principles calculations, Itoh et al. showed that K4 carbon is metallic and metastable with respect to graphite and diamond. A possible conversion pathway from graphite was also proposed [1]. However, the investigation reported in Ref. [1] failed to establish the stability unequivocally and, therefore, the possible existence of this material. |
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