温和压力范围内的超导三元化合物Li-X-B（X=Mo、W）：第一性原理预测
Superconducting ternary compounds Li-X-B (X=Mo, W) within the mild pressure range: First-principles predictions
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中文总结 AI 辅助
本研究结合第一性原理计算与晶体结构预测，提出三元成分线（TCLs）策略，预测得到Li-X-B（X=Mo、W）体系的多种超导三元化合物，将稳定超导压力降至0 GPa，初步验证了TCLs策略的有效性。
中文摘要 AI 辅助
在高压下的超导氢化物中，大量研究聚焦于三元化合物以探索独特的超导体，这类超导体能够降低稳定所需的压力并维持超导性。本工作为验证所提出的用于探索三元化合物的三元成分线（TCLs）策略，结合第一性原理计算与晶体结构预测，研究高压下的三元化合物Li-X-B（X=Mo、W）。沿Li-W-B体系的5条TCLs和Li-Mo-B体系的4条TCLs计算后，共预测得到5种Li-W-B化合物和4种Li-Mo-B化合物。其中LiWB4、Li4MoB2和LiMo2B2的组成在高压下热力学稳定；Li2WB6在0 GPa时凸包能量约为0.02 eV/atom，具备合成潜力。预测得到的Li2WB6（空间群P6/mmm）和Li2WB4（空间群R-3m）均具有超导性，其Tc约为11 K，与WB2（空间群P6/mmm）在约100 GPa下的Tc（约100 K）相近。研究还发现Li4MoB2（空间群C2/m）在压缩时出现Tc异常升高的现象。为评估TCLs策略在0 GPa下Li-W-B体系的有效性，本研究开展了全三元搜索（FTS）。研究结果有助于理解高压下Li-X-B（X=Mo、W）的相图，引入Li原子提供了候选结构，将WB2（空间群P6/mmm）所需的稳定压力从约100 GPa降至0 GPa；同时初步验证了TCLs策略在结构预测中的有效性，未来有望改进该策略，为三元化合物研究提供新思路。
英文摘要
Among the superconducting hydrides under high pressure, a number of studies concentrate on the ternary compounds to explore unique superconductors, which are capable of reducing the stable pressure and maintain superconductivity. In this work, to verify our proposed strategy of ternary composition lines (TCLs) to explore ternary compounds, we combined the first-principles calculations and crystal structure predictions to study the ternary compounds Li-X-B (X=Mo, W) under high pressure. After calculations along five and four TCLs in Li-W-B and Li-Mo-B, respectively, five Li-W-B compounds and four Li-Mo-B compounds were predicted. The compositions of LiWB4, Li4MoB2 and LiMo2B2 could be thermodynamically stable under high pressure, and Li2WB6 is around 0.02 eV/atom above the convex hull at 0 GPa, which has potential for synthesizing. Both of the predicted Li2WB6 P6/mmm and Li2WB4 R-3m are superconducting and their Tc are around 11 K, which are similar to the Tc of WB2 P6/mmm around 100 GPa. An anomalous increase of Tc was found in Li4MoB2 C2/m upon compression. We carried out full ternary search (FTS) to evaluate the validity of the TCLs strategy in Li-W-B system at 0 GPa. Our results are helpful for understanding the phase diagram of Li-X-B (X=Mo, W) under high pressure and the introducing of Li atoms provide candidate structures to reduce the measured stable pressure from ~100 GPa in WB2 P6/mmm to 0 GPa. Meanwhile, we preliminary validate the strategy of TCLs in structure predictions and we expect to improve this strategy in the future, shedding light on the studies of ternary compounds.
