Crystal structure evolution and superconductivity of YBH8 under pressure from first principles

Abstract

Reducing the stability pressure and enhancing superconductivity are the current missions in the research on superconducting hydrides. Rare-earth borohydrides have attracted extensive attention in very recent years. Using CALYPSO methodology and first-principles calculations, we investigated pressure-dependent behaviors of YBH₈ borohydride compounds. P2₁/m-YBH₈ is stable at 100–160 GPa, transitioning to C2/c-YBH₈ stable at 160–300 GPa. Dual bonding in BH_n units and metallic nature of both structures were confirmed. C2/c-YBH₈ʼs superconducting transition temperature exceeds 70 K at 200 GPa and 72 K at 300 GPa, mainly due to BH₆ units. This research contributes to understanding ytterbium-based borohydrides and provides a reference for future experiments and superconductivity investigations.