npj: 高熵合金—电子散射机制
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虽然人们早就知道位错严重影响输运性能，但最近对一系列固溶体3d-过渡金属合金的测量结果显示，残余电阻率有两个数量级的差异，其机制如何尚未见报道。
由美国橡树岭国家实验室的George Malcom Stocks领导团队，使用从头算方法研究了Cantor-Wu族面心立方无序合金残余电阻率差异背后的电子散射机制。虽然所有合金的载流子密度都与普通金属一样高，但电子平均自由程可以从~10 Å（强散射极限）到~103 Å（弱散射极限）变化。为探讨导致这样不同行为的潜在电子散射机制，他们首先模拟再现了实验观察到的结果，即含有锰和铬的合金具有高的残余电阻率，而所有其他Cantor-Wu合金都只有低的残余电阻率。虽然位点对角线、自旋相关、潜在散射总是占据主导地位，但对于仅含Fe、Co和Ni的合金，多数自旋通道经历的无序散射可以忽略，从而提供了短路，而对于含Cr或 Mn的合金，两者都具有自旋通道，由于电子填充效应而经历了强无序散射。单位点电子散射与磁性引起的散射相结合，显示这一现象是由于锰和铬引起费米表面因半填充的d带而导致的涂抹。有些令人惊讶的是，其他一些散射机制——包括位移效应或尺寸效应，散射已被证明与诸如屈服强度之类的各种性质有强相关性——现在却被发现在大多数情况下都是相对较弱的相关性。深入理解无序合金中的电子传输，将有助于阐明它们更具奇特的性质。
该文近期发表于npj Computational Materials 5: 1 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。
Uncovering electron scattering mechanisms in NiFeCoCrMn derived concentrated solid solution and high entropy alloys
Sai Mu, German D. Samolyuk, Sebastian Wimmer, Maria C. Troparevsky, Suffian N. Khan, Sergiy Mankovsky, Hubert Ebert & George M. Stocks
Whilst it has long been known that disorder profoundly affects transport properties, recent measurements on a series of solid solution 3d-transition metal alloys reveal two orders of magnitude variations in the residual resistivity. Using ab initio methods, we demonstrate that, while the carrier density of all alloys is as high as in normal metals, the electron mean-free-path can vary from ~10 Å (strong scattering limit) to ~103 Å (weak scattering limit). Here, we delineate the underlying electron scattering mechanisms responsible for this disparate behavior. While site-diagonal, spin dependent, potential scattering is always dominant, for alloys containing only Fe, Co, and Ni the majority-spin channel experiences negligible disorder scattering, thereby providing a short circuit, while for Cr/Mn containing alloys both spin channels experience strong disorder scattering due to an electron filling effect. Somewhat surprisingly, other scattering mechanisms—including displacement, or size effect, scattering which has been shown to strongly correlate with such diverse properties as yield strength—are found to be relatively weak in most cases.
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