Lin Weixiao, Xue Zefan, Cui Wenjun, Kulovits Andreas, Ren Hao, Zhao Wen, Wu Jinsong, Van Tendeloo Gustaaf, Wiezorek Jörg, Sang Xiahan
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China.
Nanostructure Research Center, Wuhan University of Technology, Wuhan, China.
Nat Commun. 2025 Jul 1;16(1):5811. doi: 10.1038/s41467-025-60966-0.
Local disorders of lattice, charge, orbital, and spin perturbate the electron density distribution in materials, profoundly influencing their properties. Consequently, experimental determination of local electron density offers a powerful, universal approach to probe such disorder. Although quantitative convergent beam electron diffraction (QCBED) is widely employed for electron density measurements in ordered crystals, its applicability to disordered structures, where the translational symmetry of the electrostatic potential is broken, remains uncertain. Here, a multi-beam off-zone axis CBED technique combined with a coherent potential approximation in Bloch wave formalism is used to simultaneously determine chemical disorder parameters, deformation electron density ∆ρ, and Debye-Waller factors (DWF) in both chemically-ordered L1 FePd and chemically-disordered γ-phase FePd solid solution. The CBED results reveal that chemical disordering significantly increases DWFs while having a negligible impact on ∆ρ. Density functional theory calculations on supercells with randomly distributed Fe and Pd atoms support these experimental findings. This work validates QCBED as a robust method for quantifying local disorder parameters in chemically disordered systems, bridging a critical gap in the characterisation of disordered materials.
晶格、电荷、轨道和自旋的局部无序会扰乱材料中的电子密度分布，从而深刻影响其性质。因此，对局部电子密度进行实验测定为探测此类无序提供了一种强大的通用方法。尽管定量会聚束电子衍射（QCBED）被广泛用于有序晶体中的电子密度测量，但其对无序结构（其中静电势的平移对称性被打破）的适用性仍不确定。在此，一种多束离区轴CBED技术与布洛赫波形式的相干势近似相结合，用于同时确定化学有序的L1 FePd和化学无序的γ相FePd固溶体中的化学无序参数、形变电子密度∆ρ和德拜-瓦勒因子（DWF）。CBED结果表明，化学无序显著增加了DWF，而对∆ρ的影响可忽略不计。对具有随机分布的Fe和Pd原子的超胞进行的密度泛函理论计算支持了这些实验结果。这项工作验证了QCBED作为一种量化化学无序系统中局部无序参数的可靠方法，弥合了无序材料表征中的一个关键差距。
