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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Unusual effects on hydrogenation: anomalous expansion and volume contraction
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Unusual effects on hydrogenation: anomalous expansion and volume contraction

机译：对氢化的异常影响：反常膨胀和体积收缩

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摘要

The present paper considers two unique volume effects associated with the formation of intermetallic hydrides, anomalously high linear and volume expansion (CeNi_3 -> CeNi_3D_(2.8)) and unusual volume contraction (HoNiSn -> HoNiSnD_(0.67)). The crystal structures of both deuterides were solved on the basis of powder neutron diffraction data. The hexagonal CeNi_3 anisotropically expands on hydrogenation along 00z (30.7 percent). In orthorhombic CeNi_3D_(2.8) (space group Pmcn (No. 62); a = 4.8748(3); b = 8.5590(5); c = 21.590(2) A) this expansion proceeds within the CeNi_2 slabs only (63.1 percent), with a 'shrinking' of the CeNi_5 parts (-2.8 percent). All D atoms are located inside the CeNi_2 part and on the border of CeNi_2 and CeNi_5. In sharp contrast to the known crystal structures of intermetallic hydrides, in CeNi_3D_(2.8) deuterium atoms do not fill initially existing interstices but, instead, attract cerium atoms into their surrounding and form new D-occupied sites, Ce_3Ni and Ce_3Ni_3. The hydrogenation of HoNiSn causes a transition from TiNiSi to the ZrNiAl type of structure. Transformation of the metallic sublattice into the ZrNiAl type results in a 'shrinking' of the Ho_3Ni tetrahedra filled by D. Their occupation in HoNiSnD_(0.67) (space group P6-bar2m (No. 189); a = 7.24197(10); c = 3.93514(7) A) proceeds with a formal 'negative' volume expansion effect and leads to the formation of strong Ho-H bonds.
机译：本文考虑了与金属间氢化物形成有关的两个独特的体积效应，即异常高的线性和体积膨胀（CeNi_3-> CeNi_3D_（2.8））和不寻常的体积收缩（HoNiSn-> HoNiSnD_（0.67））。根据粉末中子衍射数据解析了两种氘化物的晶体结构。六角形的CeNi_3在氢化时沿00z各向异性膨胀（30.7％）。在正交晶体CeNi_3D_（2.8）（空间群Pmcn（No. 62）; a = 4.8748（3）; b = 8.5590（5）; c = 21.590（2）A）中，这种膨胀仅在CeNi_2平板内进行（63.1％） ，CeNi_5零件“缩小”（-2.8％）。所有D原子都位于CeNi_2部分内部以及CeNi_2和CeNi_5的边界上。与已知的金属间氢化物的晶体结构形成鲜明对比的是，在CeNi_3D_（2.8）中，氘原子并不填充最初存在的空隙，而是将铈原子吸引到其周围并形成新的D占据位置Ce_3Ni和Ce_3Ni_3。 HoNiSn的氢化导致从TiNiSi过渡到ZrNiAl型结构。金属亚晶格转变为ZrNiAl型导致D填充的Ho_3Ni四面体``收缩''。它们在HoNiSnD_（0.67）中的占据（空间群P6-bar2m（编号189）; a = 7.24197（10）; c = 3.93514（7）A）进行正式的“负”体积膨胀效应，并导致形成坚固的Ho-H键。

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