First principles analysis of surface dependent segregation in bimetallic alloys
First principles analysis of surface dependent segregation in bimetallic alloys
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DOI：
10.1039/c9cp03984h
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发表时间：
2019-11-14
影响因子：
3.3
通讯作者：
Deskins, N. Aaron
中科院分区：
文献类型：
--
作者：
Farsi, Lida;Deskins, N. Aaron
稳定性是合金的一个重要方面，并且所提出的合金可能由于不利的原子相互作用而不稳定。合金的偏析可能优先发生在特定的暴露表面，这可能影响合金的结构，因为某些表面可能富含某些元素。使用密度泛函理论（DFT），我们模拟了表面偏析的合金，涉及所有的过渡金属掺杂的Pt，Pd，Ir和Rh。我们不仅模拟了这些合金的常见（111）面，而且还模拟了这些合金的（100）、（110）和（210）面。对于早过渡金属和晚过渡金属来说，偏析是更优选的，而中过渡金属在母体金属中最稳定。我们发现这些一般的趋势偏析能量的母体金属：Pt > Rh > Pd > Ir。不同的表面的比较表明没有一致的趋势，在不同的母体主机，但偏析能量可以变化高达2 eV，这取决于暴露的表面。我们还开发了一个统计模型来预测表面依赖的偏析能。我们的模型是能够区分偏析在不同的表面（而不是一般的偏析常见于以前的模型），并同意与DFT数据。本研究提供了有价值的信息，表面依赖偏析，并有助于解释为什么某些合金结构的发生（如核壳）。
Stability is an important aspect of alloys, and proposed alloys may be unstable due to unfavorable atomic interactions. Segregation of an alloy may occur preferentially at specific exposed surfaces, which could affect the alloy's structure since certain surfaces may become enriched in certain elements. Using density functional theory (DFT), we modeled surface segregation in bimetallic alloys involving all transition metals doped in Pt, Pd, Ir, and Rh. We not only modeled common (111) surfaces of such alloys, but we also modeled (100), (110), and (210) facets of such alloys. Segregation is more preferred for early and late transition metals, with middle transition metals being most stable within the parent metal. We find these general trends in segregation energies for the parent metals: Pt > Rh > Pd > Ir. A comparison of different surfaces suggests no consistent trends across the different parent hosts, but segregation energies can vary up to 2 eV depending on the exposed surface. We also developed a statistical model to predict surface-dependent segregation energies. Our model is able to distinguish segregation at different surfaces (as opposed to generic segregation common in previous models), and agrees well with the DFT data. The present study provides valuable information about surface-dependent segregation and helps explain why certain alloy structures occur (e.g. core-shell).