新型LiB化合物晶体结构和形貌研究

Crystal structure and morphology of a new compound LiB

3.3 电子密度函数分析 电子密度函数的计算是确定晶胞内电子云分布情况最好的方法,它可以使键性和结构的测定更为精确。

Crystal structure and morphology of LiB compound, used as refractory frame in the advanced thermal battery anode of Li-B alloys, have been determined. The completed X-ray diffraction (XRD) spectrum of LiB has been obtained. Through computation of XRD spectrum intensity and analysis of electron density function, the crystal structure of the compound have been determined. Its composition is LiB, with hexagonal structure, α = 0.402 2 nm and c = O. 2796 nm. It belongs to space group No. 194 P 6_3/m 2/m 2/c· Atom positions in unit cell are B_1: (0,0,0), B_2: (0,0, 1/2), Li_1: (2/3, 1/3, 0) and Li_2: (1/3,2/3,1/2). Theoretical density of the compound is 1.50 g/cm^3. Analysis of electron density function shows that in the compound the lithium is in the state of Li^+ and boron atoms are covalently bonded. SEM results indicate that the compound is in the form of·fiber. After rolling, the LiB fibers align along the rolling direction. The data of X-ray photography and XRD show that Li-B alloy is characteristic of texture and that its diffraction patterns are fitted well with theoretical prediction.