Super-hard and superconducting boron clathrates in the prediction of U-B compounds

TL;DR

This study predicts new uranium-boron compounds with layered and cage structures, some of which are super-hard and superconducting, expanding the understanding of binary borides under high pressure.

Contribution

It introduces four novel U-B stoichiometries and three boron clathrates at ambient pressure, combining first-principles calculations with crystal structure prediction.

Findings

C2/m-B6 has a Vickers hardness of 49-53 GPa

C2/m-B12 is superconducting with Tc of 16.12 K

Predicted compounds enrich the phase diagram of borides

Abstract

The binary metal borides provide a promising platform for searching unique materials with superconductivity and super-hardness under high pressure, owing to the distinctive bonding characters of boron. In this work, combined the first-principles calculations and crystal structure predictions, we predicted 4 exotic stoichiometries and 8 unique U-B compounds under high pressure. The predicted compounds have layered or caged structure units and 4 of them host high hardness under ambient pressure. By removal of the U atoms, we predicted three meta-stable boron clathrates at ambient pressure. Remarkably, the Vickers hardness of the predicted C2/m-B6 is estimated to be 49-53 GPa, and the C2/m-B12 is superconducting with the Tc value of 16.12 K. Our calculations enrich the phase diagram of binary metal borides and boron allotropes, providing insights for the future theoretical and experimental studies on unique materials.