Hard BN Clathrate Superconductors.

The search for hard superconductive materials has attracted a great deal of attention due to their fundamentally interesting properties and potentially practical applications. Here we predict a new class of materials based on sodalite-like BN frameworks, X(BN)6, where X = Al, Si, Cl, etc. Our simulations reveal that these materials could achieve high superconducting critical temperatures ( Tc) and high hardness. Electron-phonon calculations indicate that Tc of these compounds varies with the doping element. For example, the superconducting Tc of sodalite-like Al(BN)6 is predicted to reach ∼47 K, which is higher than that in the renowned MgB2 (39 K). This phase and a series of other sodalite-based superconductors are predicted to be metastable phases but are dynamically stable as well. These doped sodalite-based structures are likely to become recoverable as potentially useful superconductors with high hardness. Our current results present a new strategy for searching for hard high- Tc materials.