A superconducting boron allotrope featuring anticlinal pentapyramids

Finding allotropes with novel structures and intriguing properties is of great interest from both fundamental and applicable standpoints. Here, we propose a hitherto unknown boron allotrope, possessing intrinsic superconductivity and hardness at ambient pressure. With the aid of swarm-intelligence structure search calculations, stable boron-rich Sr-B binary compounds at high pressures were explored. In addition to the known SrB6, an orthogonal compound, SrB8, which is stable above 134.6 GPa was found. Its remarkable structural feature is that it contains a channel-like boron covalent framework constituted of anticlinal pentapyramids. More interestingly, the removal of Sr atoms, located at the center of the channel, leads to the formation of a novel o-B-16 boron allotrope at ambient pressure. It is metallic with a superconducting transition temperature of 14.2 K. In addition, o-B-16 demonstrates an inherently hard nature with an estimated Vickers hardness of 19.4 GPa.

Automated summary

Researchers have discovered a novel boron allotrope with intrinsic superconductivity and hardness at high pressure, as well as a new o-B-16 boron allotrope with metallic properties and a superconducting transition temperature of 14.2 K.