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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Search for Pnma materials with high-temperature structural phase transitions
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Search for Pnma materials with high-temperature structural phase transitions

机译：寻找具有高温结构相变的Pnma材料

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摘要

A systematic search for structures having a high-temperature structural phase transition can be carried out through the identification in the structural databases of those structures that can be considered pseudosymmetric. Pseudosymmetry in a crystal structure indicates the possibility of a similar configuration of higher symmetry. If the distortion relating both structures is small enough, it can be expected that the crystal acquires the more symmetric configuration through a Landau-type phase transition at a higher temperature. Here, we present the results of such a search among inorganic structures with space group Pnma retrieved from the Inorganic Crystal Structure Database. Pseudosymmetry has indeed been detected in those compounds with a known (displacive) Landau-type phase transition at higher temperatures. This is measured by a parameter Delta, which measures the maximal atomic displacement relating the pseudosymmetry-transformed structure and the original one. In most of these compounds with a known phase transition, this parameter was smaller than 1.0 Angstrom for at least one minimal supergroup of Pnma. The database contains 144 additional structures with pseudosymmetry features under the same quantitative limit. A comparison of the Delta distributions in both sets of compounds suggests a smaller Delta window (with 0.7 Angstrom as maximal value) for selecting the materials having maximal probability of exhibiting a phase transition at higher temperatures. A set of 58 compounds fulfils this criterion. [References: 22]
机译：通过在结构数据库中识别那些可以被认为是伪对称的结构，可以对具有高温结构相变的结构进行系统搜索。晶体结构中的伪对称性表明可能具有更高对称性的类似构型。如果两个结构的畸变足够小，则可以预期晶体通过在较高温度下的Landau型相变而获得更对称的构型。在这里，我们提出了从无机晶体结构数据库中检索到的具有空间群Pnma的无机结构的搜索结果。确实在那些在较高温度下具有已知（置换）Landau型相变的化合物中检测到了伪对称性。这是通过参数Delta来测量的，该参数测量与伪对称变换的结构和原始结构相关的最大原子位移。在大多数具有已知相变的化合物中，对于至少一个最小的Pnma超群，此参数小于1.0埃。该数据库包含144个具有相同定量限制下的伪对称特征的其他结构。两组化合物中Delta分布的比较表明，较小的Delta窗口（最大值为0.7埃）用于选择在较高温度下具有最大相变可能性的材料。一组58种化合物满足此标准。 [参考：22]

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