论文标题
离子量子波动对LABH $ _8 $的热力学稳定性和超导性的影响
Impact of ionic quantum fluctuations on the thermodynamic stability and superconductivity of LaBH$_8$
论文作者
论文摘要
最近对亚稳态的高对称性FM $ \ bar {3} $ m相的预测，可以在富含三元氢的化合物的负担压力下达到高超管的临界温度。利用密度功能理论中的第一原理计算和随机自洽的谐波近似，我们确定离子量子波动使系统动态不稳定在77 GPA以下，其压力比45 GPA高于经典的GPA高得多。量子Anharmonic效应拉伸了结构的BH $ _8 $单位中的共价B-H键，因此，软化了所有氢 - 特性模式。高于77 GPA FM $ \ bar {3} $ m labh $ _8 $保持稳定，有趣的是，它的超导临界温度在很大程度上通过量子性静脉效应增强，在动态不稳定性的边缘达到了约170 K的临界温度。我们的结果表明，具有共价键合的对称XH $ _8 $单位的低压亚稳态阶段将因离子量子波动而不稳定。
The recent prediction of a metastable high-symmetry Fm$\bar{3}$m phase of LaBH$_8$ gives hopes to reach high superconducting critical temperatures at affordable pressures among ternary hydrogen-rich compounds. Making use of first-principles calculations within density functional theory and the stochastic self-consistent harmonic approximation, we determine that ionic quantum fluctuations drive the system dynamically unstable below 77 GPa, a much higher pressure than the 45 GPa expected classically. Quantum anharmonic effects stretch the covalent B-H bond in the BH$_8$ units of the structure and, consequently, soften all hydrogen-character modes. Above 77 GPa Fm$\bar{3}$m LaBH$_8$ remains metastable and, interestingly, its superconducting critical temperature is largely enhanced by quantum anharmonic effects, reaching critical temperatures around 170 K at the verge of the dynamical instability. Our results suggest that low pressure metastable phases with covalently bonded symmetric XH$_8$ units will be destabilized by ionic quantum fluctuations.
