The characterization of simple elemental systems is key to benchmarking first-principles modeling of electronic and vibrational behaviors of materials. A large body of literature has been built for most elemental systems in the periodic table. However, surprisingly little neutron work has been performed to probe the vibrational properties of iridium, likely due to its large neutron absorption cross section. Nonetheless, iridium is of significant scientific and technological interest due to large relativistic electron effects and electron-phonon coupling, particularly in strongly correlated iridate compounds. Here, we report temperature-dependent inelastic neutron scattering measurements of the vibrational properties of iridium, from which we extract key thermodynamic properties. To overcome the challenge of the large neutron absorption of iridium, we developed a simple postprocessing correction procedure. The measured densities of phonon states compare well with quasiharmonic density functional theory calculations, although the obtained experimental phonon Grüneisen parameters are much larger than expected, reaching as high as $\gamma =4.5$, indicating substantial anharmonicity.

中文翻译：

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铱中随温度变化的晶格动力学

简单元素系统的表征是基准测试材料电子和振动行为的第一性原理模型的关键。对于元素周期表中的大多数元素系统，已经建立了大量文献。但是，出乎意料的是，由于铱的中子吸收截面大，几乎没有进行中子功来探测铱的振动特性。尽管如此，由于大的相对论性电子效应和电子-声子耦合，特别是在强相关的铱酸盐化合物中，铱具有重要的科学技术意义。在这里，我们报告铱的振动特性的温度相关的非弹性中子散射测量结果，从中我们提取出关键的热力学特性。为了克服铱吸收大量中子的挑战，我们开发了一个简单的后处理校正程序。测得的声子态密度与准谐波密度泛函理论计算结果很好地比较，尽管获得的实验声子Grüneisen参数远大于预期，达到了$\gamma =4.5$，表明存在严重的非谐性。