Mode decomposition based on crystallographic symmetry in the band-unfolding method
Mode decomposition based on crystallographic symmetry in the band-unfolding method
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DOI：
10.1103/physrevb.95.024305
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发表时间：
2017-01-13
影响因子：
3.7
通讯作者：
Tanaka, Isao
中科院分区：
文献类型：
--
作者：
Ikeda, Yuji;Carreras, Abel;Tanaka, Isao
带展开方法是从无序体系的超原胞模型出发计算其有效能带结构的一种常用方法。未折叠的能带结构显示了潜在结构的晶体学对称性，其中化学组分的差异和局部原子弛豫被忽略。然而，仍然难以将未折叠的能带结构分解成基于基础结构的晶体学对称性的模式，因此，未折叠的能带结构的详细分析受到限制。在这项研究中，一个程序来分解的展开带结构根据小集团的小表示（SR）。分解是使用来自群表示理论的SR的投影算子进行的。本文采用目前的方法研究了无序面心立方Cu_（0.75）Au_（0.25）的声子能带结构，由于化学无序，Cu_（0.75）Au_（0.25）的原子质量和原子力常数在原子位置之间有很大的变化.在展开的声子带结构中，对应于特定的共振谱，分解模中出现了一些特殊的行为，如不连续和分裂分支。它们的出现是因为化学元素的不同组合导致了不同的频率区域。
The band-unfolding method is widely used to calculate the effective band structures of a disordered system from its supercell model. The unfolded band structures show the crystallographic symmetry of the underlying structure, where the difference of chemical components and the local atomic relaxation are ignored. However, it has still been difficult to decompose the unfolded band structures into the modes based on the crystallographic symmetry of the underlying structure, and therefore detailed analyses of the unfolded band structures have been restricted. In this study, a procedure to decompose the unfolded band structures according to the small representations (SRs) of the little groups is developed. The decomposition is performed using the projection operators for SRs derived from the group representation theory. The current method is employed to investigate the phonon band structure of disordered face-centered-cubic Cu0.75Au0.25, which has large variations of atomic masses and force constants among the atomic sites due to the chemical disorder. In the unfolded phonon band structure, several peculiar behaviors such as discontinuous and split branches are found in the decomposed modes corresponding to specific SRs. They are found to occur because different combinations of the chemical elements contribute to different regions of frequency.