Synthesis and crystal structure of tetragonal LnMg2H7 (Ln=La, Ce), two Laves phase hydride derivatives having ordered hydrogen distribution
Synthesis and crystal structure of tetragonal LnMg2H7 (Ln=La, Ce), two Laves phase hydride derivatives having ordered hydrogen distribution
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具有有序氢分布的两种Laves相氢化物衍生物四方LnMg2H7 (Ln=La, Ce)的合成和晶体结构
DOI：
10.1016/s0925-8388(96)02992-1
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发表时间：
1997
影响因子：
6.2
通讯作者：
A. Hewat
中科院分区：
文献类型：
--
作者：
F. Gingl;K. Yvon;T. Vogt;A. Hewat
在373 K（Ln=La）和423 K（Ln=Ce）和100 bar氢（氘）压下，通过氢化（氘化）LnMg 2，合成了LaMg 2 H7和CeMg 2 H7及其氘化物。它们的金属亚结构代表了立方C15 Laves相结构的一种新的四方畸变变体，空间群为P41212（No.92）; LaMg 2 H7的晶胞参数：a=6.4054（2）Ω，c=9.5994（3）Ω; LaMg 2D 7：a=6.3900（2）Ω，c=9.5782（4）Ω; CeMg 2 H7：a=6.3663（3）Ω，c=9.5226（5）Ω; CeMg 2D 7：a=6.3501（3）μ m，c=9.4957（5）μ m; Z=4。氢（氘）分布由四个对称性独立的完全占据的位点组成，其具有三角形[Ln 2 Mg]和四面体[Ln 2 Mg 2]和[Mg 4]金属配位，距离范围为La-D=2.39-2.55 μ m; Ce-D=2.36-2.51 μ m; Mg-D=1.92-2.13 μ m（La），1.91-2.18 μ m（Ce）。氢与金属的比率，H/M=7/3，是迄今为止报道的Laves相氢化物衍生物的最高值。
LaMg2H7, CeMg2H7and their deuterides were synthesized by hydrogenation (deuteration) of binary LnMg2at 373 K (Ln=La) and 423 K (Ln=Ce) and 100 bar hydrogen (deuterium) pressure and characterized by X-ray and neutron powder diffraction at room temperature. Their metal substructure represents a new tetragonal distortion variant of the cubic C15 Laves phase structure, space group P41212 (No. 92); cell parameters for LaMg2H7: a=6.4054(2) Å, c=9.5994(3) Å; LaMg2D7: a=6.3900(2) Å, c=9.5782(4) Å; CeMg2H7: a=6.3663(3) Å, c=9.5226(5) Å; CeMg2D7: a=6.3501(3) Å, c=9.4957(5) Å; Z=4. The hydrogen (deuterium) distribution consists of four symmetry independent, fully occupied sites having triangular [Ln2Mg] and tetrahedral [Ln2Mg2] and [Mg4] metal coordinations with distances in the range La–D=2.39–2.55 Å; Ce–D=2.36–2.51 Å; Mg–D=1.92–2.13 Å (La), 1.91–2.18 Å (Ce). The hydrogen-to-metal ratio, H/M=7/3, is the highest reported so far for Laves phase hydride derivatives.