Theoretical predictions of MB5N5: Atom-stuffed boronitride clathrate cages derived from the high-pressure superhydrides

This study investigates 198 $M{X}_5{Y}_5$ ($X$, $Y$ = B, C, or N) clathrate-like structures derived from $M$H₁₀ superhydrides using high-throughput Density Functional Theory (DFT) geometry optimizations and phonon calculations. A wide variety of electropositive and electronegative encapsulated atoms were considered. From all of the studied systems only 34 $M$B${}_5$N${}_5$ phases were found to be dynamically stable at ambient pressure. The highest 1-atmosphere superconducting critical transition temperature was predicted for FB${}_5$N${}_5$. However, ab initio molecular dynamics simulations revealed that all of the identified superconducting phases decompose by 300 K at 1 atm, while only eleven semiconducting phases remained thermally stable. Our findings underscore the critical role of kinetic and thermal stability in predicting viable superconductors. The electronic structure of the $M$B${}_5$N${}_5$ compounds were rationalized in terms of electron donating and withdrawing intercalants. DFT and machine-learning based predictions of their mechanical properties were compared with those of an empty boronitride cage.