Laves相LnMg <sub>2</sub>（Ln = La，Ce，Pr，Nd，Sm，Eu，Gd，Tb，Ho，Er，Tm，Yb）的氢化性质,Inorganic Chemistry

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Laves相LnMg ₂（Ln = La，Ce，Pr，Nd，Sm，Eu，Gd，Tb，Ho，Er，Tm，Yb）的氢化性质
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-11-22 00:00:00 , DOI: 10.1021/acs.inorgchem.7b02319
Anton Werwein ₁ , Florian Maaß ₁ , Leonhard Y. Dorsch ₁ , Oliver Janka ₂ , Rainer Pöttgen ₂ , Thomas C. Hansen ₃ , Justin Kimpton ₄ , Holger Kohlmann ₁

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通过热分析，X射线，同步加速器和中子粉末研究了Laves相LnMg ₂（Ln = La，Ce，Pr，Nd，Sm，Eu，Gd，Tb，Ho，Er，Tm，Yb）的氢化性质衍射。在14.0兆帕的氢气压力和393 K，PrMg ₂和NdMg ₂占用氢和形成无色的，三元的氢化物PrMg ₂ ħ ₇（P 4 ₁ 2 ₁ 2，一个= 632.386（6）时，C ^ = 945.722（11 ）pm）和NdMg ₂ H ₇（P 4 ₁ 2 ₁ 2 a = 630.354（9）pm，c= 943.018（16）pm）。晶体结构通过Rietveld方法从氘核上的中子粉末衍射数据（PrMg ₂ D ₇，P 4 ₁ 2 ₁ 2 a = 630.56（2）pm，c = 943.27（3）pm; NdMg ₂ D ₇，P 4 ₁ 2 ₁ 2，a = 628.15（2）pm，c = 940.32（3）pm），显示与LaMg ₂ D ₇同型。LaMg ₂ D ₇氢化物类型分别在695 K（La），684 K（Ce），684 K（Pr），672 K（Nd）和639 K（Sm）分解为镧系元素氢化物和镁。Laves相EuMg ₂形成黑色的氢化物EuMg ₂ H _x。它的晶体结构（P 2 ₁ 2 ₁ 2 ₁，a = 664.887（4）pm，b = 1136.993（7）pm，c = 1069.887（7）pm）与六方Laves相（MgZn ₂型）密切相关。无氢母体金属间化合物。GdMg ₂和TbMg ₂与正交晶胞形成氢化物GdMg ₂ H _x（a = 1282.7（4）pm，b = 572.5（2）pm，c = 881.7（2）pm）和TbMg ₂ H _x（a = 617.8（3）pm，b = 1045.8（8）pm，c = 997.1（ 5）pm），大概也具有扭曲的MgZn ₂型结构。CeMg ₂ ħ ₇和NdMg ₂ ħ ₇是顺磁性与μ为2.49（1）有效磁矩_乙和3.62（1）μ_乙分别，与自由三价稀土阳离子的计算磁矩一致（μ_钙（Ce ³⁺）= 2.54μ_B ; μ_计算值（ND ³⁺）= 3.62μ_乙）。

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Hydrogenation Properties of Laves Phases LnMg2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb)

The hydrogenation properties of Laves phases LnMg₂ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb) were investigated by thermal analysis, X-ray, synchrotron, and neutron powder diffraction. At 14.0 MPa hydrogen gas pressure and 393 K, PrMg₂ and NdMg₂ take up hydrogen and form the colorless, ternary hydrides PrMg₂H₇ (P4₁2₁2, a = 632.386(6) pm, c = 945.722(11) pm) and NdMg₂H₇ (P4₁2₁2, a = 630.354(9) pm, c = 943.018(16) pm). The crystal structures were refined by the Rietveld method from neutron powder diffraction data on the deuterides (PrMg₂D₇, P4₁2₁2, a = 630.56(2) pm, c = 943.27(3) pm; NdMg₂D₇, P4₁2₁2, a = 628.15(2) pm, c = 940.32(3) pm) and shown to be isotypic to LaMg₂D₇. The LaMg₂D₇ type of hydrides decompose at 695 K (La), 684 K (Ce), 684 K (Pr), 672 K (Nd), and 639 K (Sm) to lanthanide hydrides and magnesium. The Laves phase EuMg₂ forms a hydride EuMg₂H_x of black color. Its crystal structure (P2₁2₁2₁, a = 664.887(4) pm, b = 1136.993(7) pm, c = 1069.887(7) pm) is closely related to the hexagonal Laves phase (MgZn₂ type) of the hydrogen-free parent intermetallic. GdMg₂ and TbMg₂ form hydrides GdMg₂H_x with orthorhombic unit cells (a = 1282.7(4) pm, b = 572.5(2) pm, c = 881.7(2) pm) and TbMg₂H_x (a = 617.8(3) pm, b = 1045.8(8) pm, c = 997.1(5) pm), presumably also with a distorted MgZn₂ type of structure. CeMg₂H₇ and NdMg₂H₇ are paramagnetic with effective magnetic moments of 2.49(1) μ_B and 3.62(1) μ_B, respectively, in good agreement with the calculated magnetic moments of the free trivalent rare-earth cations (μ_calc(Ce³⁺) = 2.54 μ_B; μ_calc(Nd³⁺) = 3.62 μ_B).

更新日期：2017-11-22

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