A valence balanced rule for discovery of 18-electron half-Heuslers with defects†,Energy & Environmental Science

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A valence balanced rule for discovery of 18-electron half-Heuslers with defects†
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2018-03-20 00:00:00 , DOI: 10.1039/c8ee00306h
Shashwat Anand _{1,

2,

3,

4} , Kaiyang Xia _{5,

6,

7,

8} , Vinay I. Hegde _{1,

2,

3,

4} , Umut Aydemir _{1,

2,

3,

4,

9} , Vancho Kocevski _{1,

2,

3,

4} , Tiejun Zhu _{5,

6,

7,

8,

10} , Chris Wolverton _{1,

2,

3,

4} , G. Jeffrey Snyder _{1,

2,

3,

4}

Affiliation

Using first-principles DFT we systematically investigate the thermodynamic stability and off-stoichiometry in 108 nominal 19-electron half-Heusler (hH) compounds. We demonstrate unambiguously that considering a cation deficiency towards the off-stoichiometric valence balanced, VEC = 18 composition is necessary for explaining the stability of all previously reported nominal VEC = 19 compounds. This is understandable in terms of an energy benefit from valence balance considering the valence of each atom using Zintl chemistry that offsets the energy penalty of forming defects in nearly all cases. Thus, we propose a valence balanced rule to understand the ground state stability of half-Heuslers irrespective of stoichiometry and nominal electron count (8, 18 or 19). Using this generalized rule we (a) predict 16 previously unreported nominal 19-electron XYZ half-Heuslers and (b) rationalize the reports of giant off-stoichiometries in compounds such as Ti_(1−x)NiSb which has been known for over 50 years. Of the 16 new compounds predicted here, Ti_(1−x)PtSb was synthesized and the half-Heusler phase confirmed through X-ray studies. The flexibility in stoichiometry of the half-Heusler systems to attain a stable valence balanced composition by accommodating large defect concentrations opens up multiple dimensions for discovery of multi-component defective half-Heuslers based on intrinsic and extrinsic defects which compensate for the nominally non-18-electron count of the structure.

中文翻译：

发现具有缺陷的18电子半霍夫斯勒的价平衡规则†

使用第一性原理DFT，我们系统地研究了108个标称19电子半赫斯勒（hH）化合物的热力学稳定性和非化学计量。我们明确地表明，考虑到朝着化学计量比平衡的阳离子缺乏，VEC = 18组成对于解释所有先前报道的标称VEC = 19化合物的稳定性是必要的。考虑到价原子平衡带来的能量收益，这是可以理解的，考虑到使用Zintl化学的每个原子的价原子能抵消几乎所有情况下形成缺陷的能量损失。因此，我们提出了一个价态平衡法则，以了解半霍斯勒分子的基态稳定性，而与化学计量和标称电子数（8、18或19）无关。_{（1 x）} NiSb已经有50多年的历史了。在这里预测的16种新化合物中，合成了Ti_{（1- x）} PtSb，并通过X射线研究证实了半霍斯勒相。Half-Heusler系统化学计量的灵活性可通过容纳较大的缺陷浓度来获得稳定的价态平衡组成，从而为发现基于内在和外在缺陷的多组分缺陷式半-Heusler开辟了多个维度，从而弥补了名义上的非18 -结构的电子数。

更新日期：2018-03-20

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