论文标题
$δ$ -bi $ _2 $ o $ $ _3 $的BI子晶格的动态障碍
Dynamic disorder in Bi sub-lattice of $δ$-Bi$_2$O$_3$
论文作者
论文摘要
$δ$ -bi $ _2 $ o $ _3 $是由于其本质上有缺陷的氟含石状结构，在O子层中具有25 \％空置位点，因此已知最快的氧化物离子导体之一。大量的衍射测量和分子动力学模拟表明，双离子构建了一个立方体，FCC晶格，并且O离子是％分布和迁移的。尽管如此，在这项研究中，我们提出了拉曼散射测量值，这些测量清楚地表明，BI子晶格保留了低温相（$α$ -bi $ _2 $ _2 $ o $ _3 $）的单斜形对称性，直至晶体的熔化温度。我们的观察结果和以前的发现之间的明显矛盾表明，双离子在有效势能表面的局部最小值之间振荡。这些最小值代表单斜相相，而时间平均结构是立方相。我们讨论了这些低频振荡对离子传导的含义。
$δ$-Bi$_2$O$_3$ is one of the fastest known solid oxide ion conductors owing to its intrinsically defective fluorite-like structure with 25\% vacant sites in the O sub-lattice. Numerous diffraction measurements and molecular dynamics simulations indicate that the Bi ions construct a cubic, fcc lattice, and the O ions are %distributing and migrating through it. Nonetheless, in this study we present Raman scattering measurements that clearly show that the Bi sub-lattice preserves the monoclinic symmetry of the low temperature phase ($α$-Bi$_2$O$_3$) up to the melting temperature of the crystal. The apparent contradiction between our observations and previous findings suggests that Bi ions oscillate between local minima of the effective potential energy surface. These minima represent the monoclinic phase while the time-averaged structure is the cubic phase. We discuss the implication of these low-frequency oscillations on ion conduction.
