Electronic Properties of a New Structure of BC2N and Its Intercalation with Magnesium: Possibility for a New High-Tc Superconductor

We propose a new structure for the graphite-like BC₂N, other than the one proposed in Liu et al. (Phys. Rev. B 39, 1760, 1989). We compare it with the older structure and show that it has a lower energy. The band structure calculations of a single sheet of this new structure show that it is a semiconductor with a very small band gap of 0.25 eV, whereas an AA stacking of BC₂N layers of this structure behaves like a metal. Because of the similarity of this structure with the boron layers in MgB₂, we propose to intercalate the layers of the new structure of BC₂N with the magnesium atoms to obtain Mg₂BC₂N. The band structure calculations of this new structure show an unusually large metallic density of states at the Fermi level, much higher than that of MgB₂. This leads us to expect Mg₂BC₂N to be a superconductor with a higher T _c.