A Synergistic Theoretical and Experimental Study on Ternary La–B–H Systems under Pressure

Ternary lanthanum borohydrides have received great interest owing to their promising superconductivity at moderate pressures. While the potential energy surfaces for these systems are rather complicated, the development of an advanced prediction method to identify the stable structures remains highly required. In this work, by employing a machine-accelerated structure prediction approach, we identified six hitherto unknown stable La-B-H compounds, including <i>Pmmn</i>-LaB₂H₆, <i>Pnma</i>-LaB₂H₁₃, <i>Pnma</i>-LaBH₇, <i>P</i>6₃/<i>mmc</i>-LaBH₈(II), <i>P</i><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover><mml:mn>1</mml:mn><mml:mo>─</mml:mo></mml:mover></mml:math>-La₂BH₁₂, and <i>Fdd</i>2-La₂BH₁₂, which contain intriguing B₂H₆, BH₄, BH₅, BH₆ and BH₈ structure motifs. To validate our theoretical results, we synthesized the predicted <i>P</i>2₁/<i>m</i>-LaB₂H₇ phase, as evidenced by the excellent agreement between theoretical and experimental X-ray diffraction data, which was further found to exhibit semiconducting behavior. Furthermore, electron-phonon coupling (EPC) simulations reveal that LaBH₇ and LaBH₈ are high-temperature superconductors, exhibiting theoretically estimated critical temperatures (<i>T</i>_c) of 102 K at 112 GPa and 104 K at 162 GPa, respectively. Our current results provide insights into the future discovery of ternary superconductors.