Computational discovery of stable and metastable ternary oxynitrides.
Computational discovery of stable and metastable ternary oxynitrides.
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稳定和亚稳定三元氮氧化物的计算发现。
DOI：
10.1063/5.0050356
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
S. Lany
中科院分区：
文献类型：
--
作者：
A. Sharan;S. Lany
根据第一原则进行的材料设计使探索未知的化学空间成为可能。人们对混合阳离子三元化合物进行了广泛的计算搜索，但混合阴离子体系也越来越引起人们的兴趣。计算发现的核心是晶体结构预测，必须在对原型结构的依赖和不受限制的采样的大小限制之间进行权衡。我们通过让两种互补的结构抽样方法竞争来应对这一挑战。我们使用动力学限制最小化方法在更小的晶胞中预测高通量的无约束晶体结构，最多可达21个原子。另一方面，三元--更广泛地说，多元--系统通常假定由二元母体结构派生的晶格上的原子有序形成的结构。因此，我们额外地在具有多达56个原子的单元的原型晶格上采样原子配置。使用这种方法，我们搜索了65个不同的电荷平衡氧化物-氮化物化学计量比，其中包括6个已知的系统作为对照样本。对热力学极限和活性氮源合成两种情况进行了凸包分析。我们确定了34个相，它们要么在凸壳上，要么在潜在亚稳态相的可行能量窗口内。我们进一步对“丢失”的二元氮化物进行了结构采样，这些氮化物的能量是凸壳分析所需的。其中，我们发现亚稳Ce3N4是四价氧化铈的氮化物类似物，在轻微活化的氮气条件下变得稳定，ΔμN>；+0.07nEV。鉴于CeO2在研究和应用中的巨大作用，Ce3N4是一个潜在的重要发现。
Materials design from first principles enables exploration of uncharted chemical spaces. Extensive computational searches have been performed for mixed-cation ternary compounds, but mixed-anion systems are gaining increased interest as well. Central to computational discovery is the crystal structure prediction, where the trade-off between reliance on prototype structures and size limitations of unconstrained sampling has to be navigated. We approach this challenge by letting two complementary structure sampling approaches compete. We use the kinetically limited minimization approach for high-throughput unconstrained crystal structure prediction in smaller cells up to 21 atoms. On the other hand, ternary-and, more generally, multinary-systems often assume structures formed by atomic ordering on a lattice derived from a binary parent structure. Thus, we additionally sample atomic configurations on prototype lattices with cells up to 56 atoms. Using this approach, we searched 65 different charge-balanced oxide-nitride stoichiometries, including six known systems as the control sample. The convex hull analysis is performed both for the thermodynamic limit and for the case of synthesis with activated nitrogen sources. We identified 34 phases that are either on the convex hull or within a viable energy window for potentially metastable phases. We further performed structure sampling for "missing" binary nitrides whose energies are needed for the convex hull analysis. Among these, we discovered metastable Ce3N4 as a nitride analog of the tetravalent cerium oxide, which becomes stable under slightly activated nitrogen condition ΔμN > +0.07 eV. Given the outsize role of CeO2 in research and application, Ce3N4 is a potentially important discovery.