Abstract Many Laves phases AM 2 takes up hydrogen to form interstitial hydrides in which hydrogen atoms partially occupy A 2 M 2, AM 3, and/or M 4 tetrahedral interstices. They often exhibit temperature-driven order-disorder phase transitions, which are triggered by repulsion of hydrogen atoms occupying neighboring tetrahedral interstices. Because of the phase widths with respect to hydrogen a complete ordering, i.e., full occupation of all hydrogen positions is usually not achieved. Order-disorder transitions in Laves phase hydrides are thus phase transitions between crystal structures with different degrees of hydrogen order. Comparing the crystal structures of ordered and disordered phases reveals close symmetry relationships in all known cases. This allows new insights into the crystal chemical description of such phases and into the nature of the phase transitions. Structural relationships for over 40 hydrides of cubic and hexagonal Laves phases ZrV2, HfV2, ZrCr2, ZrCo2, LaMg2, CeMg2, PrMg2, NdMg2, SmMg2, YMn2, ErMn2, TmMn2, LuMn2, Lu0.4Y0.6Mn2 YFe2, and ErFe2 are concisely described in terms of crystallographic group-subgroup schemes (Bärnighausen trees) covering 32 different crystal structure types, 26 of which represent hydrogen-ordered crystal structures.

中文翻译：

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Laves 相氢化物中的氢序

摘要 许多 Laves 相 AM 2 吸收氢形成间隙氢化物，其中氢原子部分占据 A 2 M 2、AM 3 和/或 M 4 四面体间隙。它们通常表现出温度驱动的有序-无序相变，这是由占据相邻四面体间隙的氢原子的排斥引发的。由于相对于氢的相位宽度，通常无法实现完全排序，即完全占据所有氢位置。因此，Laves 相氢化物中的有序-无序转变是具有不同氢有序度的晶体结构之间的相转变。比较有序和无序相的晶体结构揭示了所有已知情况下的密切对称关系。这使得对这些相的晶体化学描述和相变性质有了新的认识。对 40 多种立方和六方 Laves 相 ZrV2、HfV2、ZrCr2、ZrCo2、LaMg2、CeMg2、PrMg2、NdMg2、SmMg2、YMn2、ErMn2、TmMn2、LuMn2、Lu0.4Y0.6Mn2、YFe2、ErMn2、在晶体学组-子组方案（Bärnighausen 树）方面，涵盖 32 种不同的晶体结构类型，其中 26 种代表氢有序晶体结构。