| 尖晶石型LiMn2O4晶体结构及锂离子筛H+/Li+交换性质研究 |
| Spinel LiMn2O4 Crystal Structure and Lithium Ion-Sieve Property of H+/Li+ Exchange |
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| 摘要: 采用密度泛函理论平面波超软赝势和广义梯度近似法对尖晶石型LiMn2O4及其锂离子筛HMn2O4的晶体结构和性质进行了从头计算。PW91泛函最为有效，Li+被H+取代后HMn2O4晶胞收缩，点阵常数从LiMn2O4的0.823 nm减小至0.799 nm，其XRD峰也相应向高角度方向明显位移。经同种格点原子的XRD分析表明，Mn、O两元素对XRD方式和强度起着决定作用。其中Li呈+1价完全离子化，可被H+彻底交换，H与周围O在等电子密度图中呈现电子云相互连接，只带有0.42个正电荷。价轨道分态密度表明，Mn-O之间强的共价键合主要归因于Mn-d和O-p在费米能级下-7.3~-1.6 eV间的轨道重叠，形成了有利于H+/Li+交换的骨架空穴隧道。阵点和空穴多面体的体积遵守如下顺序：V8a>V48f>V8b、V16c>V16d、V16c>V48f。Li+最易迁移至邻近的16c位置，碱金属离子的交换受到离子半径和作用能大小的限制。 |
| 关键词: LiMn2O4 XRD计算 分态密度 电子布居 离子筛 |
| 基金项目: |
| Abstract: The crystal structures and properties of spinel-type LiMn2O4 and lithium ion-sieve HMn2O4 were investigated by using the plane-wave ultrasoft pseudopotential and the generalized gradient approximation based on density functional theory. The PW91 functional was the most beneficial. HMn2O4 unit cell contracted after Li+ was substituted by H+, the lattice constant decreased to 0.799 nm from 0.823 nm of LiMn2O4, and the XRD peaks also obviously shifted toward high angle correspondingly. According to the XRD analyses of homologous lattice atoms, we concluded that two elements Mn and O play a decisive role in the XRD mode and intensity. Among them, Li presents +1 valence and is completely ionized, and can be exchanged by H+ thoroughly; while H displays the mutual connections of electron clouds with ambient O in the isoelectronic density map, and only takes 0.42 positive charge. Atomic partial densities of states show that the strong covalent bonding between Mn-O is mainly attributed to the orbital overlap of Mn-d and O-p between -7.3~-1.6 eV below the Fermi level, and forms the hole tunnels of framework that are beneficial to ion exchange. The volumes of lattice point and hole polyhedrons comply with the following sequences: V8a>V48f>V8b, V16c>V16d, V16c>V48f. Li+ is most apt to migrate to an adjacent 16c position, and alkali metal ion exchanges are subjected to the limitation of ionic radius and the size of acting energy. |
| Keywords: LiMn2O4 XRD calculation partial density of state electronic population ion-sieve |
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| 刘肖丽,杨立新,邬赛祥,李 芬.尖晶石型LiMn2O4晶体结构及锂离子筛H+/Li+交换性质研究[J].无机化学学报,2012,28(8):1673-1679. |
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