Mulliken Center for Theoretical Chemistry, Universität Bonn, Bonn, Germany.
J Phys Condens Matter. 2012 May 23;24(20):203201. doi: 10.1088/0953-8984/24/20/203201. Epub 2012 Apr 27.
We review recent theoretical studies on ion diffusion in (Li(2)O)(x)(B(2)O(3))(1-x) compounds and at the interfaces of Li(2)O :B(2)O(3) nanocomposite. The investigations were performed theoretically using DFT and HF/DFT hybrid methods with VASP and CRYSTAL codes. For the pure compound B(2)O(3), it was theoretically confirmed that the low-pressure phase B(2)O(3)-I has space group P3(1)21. For the first time, the structure, stability and electronic properties of various low-index surfaces of trigonal B(2)O(3)-I were investigated at the same theoretical level. The (101) surface is the most stable among the considered surfaces. Ionic conductivity was investigated systematically in Li(2)O, LiBO(2), and Li(2)B(4)O(7) solids and in Li(2)O:B(2)O(3) nanocomposites by calculating the activation energy (E(A)) for cation diffusion. The Li(+) ion migrates in an almost straight line in Li(2)O bulk whereas it moves in a zig-zag pathway along a direction parallel to the surface plane in Li(2)O surfaces. For LiBO(2), the migration along the c direction (E(A) = 0.55 eV) is slightly less preferable than that in the xy plane (E(A) = 0.43-0.54 eV). In Li(2)B(4)O(7), the Li(+) ion migrates through the large triangular faces of the two nearest oxygen five-vertex polyhedra facing each other where E(A) is in the range of 0.27-0.37 eV. A two-dimensional model system of the Li(2)O :B(2)O(3) interface region was created by the combination of supercells of the Li(2)O (111) surface and the B(2)O(3) (001) surface. It was found that the interface region of the Li(2)O:B(2)O(3) nanocomposite is more defective than Li(2)O bulk, which facilitates the conductivity in this region. In addition, the activation energy (E(A )) for local hopping processes is smaller in the Li(2)O :B(2)O(3) nanocomposite compared to the Li(2)O bulk. This confirms that the Li(2)O:B(2)O(3) nanocomposite shows enhanced conductivity along the phase boundary compared to that in the nanocrystalline Li(2)O.
我们回顾了最近关于（Li(2)O)(x)(B(2)O(3))(1-x) 化合物和 Li(2)O:B(2)O(3) 纳米复合材料界面中离子扩散的理论研究。这些研究是使用 DFT 和 HF/DFT 混合方法，使用 VASP 和 CRYSTAL 代码在理论上进行的。对于纯化合物 B(2)O(3)，理论上证实了低压相 B(2)O(3)-I 的空间群为 P3(1)21。首次在相同的理论水平上研究了各种低指数三角 B(2)O(3)-I 表面的结构、稳定性和电子性质。在所考虑的表面中，(101) 表面是最稳定的。通过计算阳离子扩散的活化能（E(A)），系统地研究了 Li(2)O、LiBO(2)、Li(2)B(4)O(7) 固体和 Li(2)O:B(2)O(3) 纳米复合材料中的离子电导率。Li(+)离子在 Li(2)O 体相中沿几乎直线迁移，而在 Li(2)O 表面中沿平行于表面平面的锯齿形路径迁移。对于 LiBO(2)，沿 c 方向的迁移（E(A) = 0.55 eV）略低于 xy 平面上的迁移（E(A) = 0.43-0.54 eV）。在 Li(2)B(4)O(7)中，Li(+)离子通过彼此相对的两个最近的氧五顶点多面体的大三角形面迁移，其中 E(A)在 0.27-0.37 eV 的范围内。通过 Li(2)O(111)表面和 B(2)O(3)(001)表面的超晶胞组合，创建了 Li(2)O:B(2)O(3) 界面区域的二维模型系统。结果表明，Li(2)O:B(2)O(3) 纳米复合材料的界面区域比 Li(2)O 体相更有缺陷，这有利于该区域的电导率。此外，与 Li(2)O 体相相比，Li(2)O:B(2)O(3) 纳米复合材料中局部跃迁过程的活化能（E(A)）较小。这证实了与纳米晶 Li(2)O 相比，Li(2)O:B(2)O(3) 纳米复合材料在相界处表现出增强的电导率。
