Simulation of Intrinsic Defects and Cd Site Occupation in LaIn3 and LuIn3
Simulation of Intrinsic Defects and Cd Site Occupation in LaIn3 and LuIn3
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DOI：
10.4028/www.scientific.net/df.27.40
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
M. Zacate;John P. Bevington;G. Collins
中科院分区：
文献类型：
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作者：
M. Zacate;John P. Bevington;G. Collins
在以前的工作中，扰动角相关谱（PAC）被用来确定跳跃率的111镉，111 In放射性示踪剂的女儿，在一系列的相位RIn 3（R =稀土元素）通过核四极杆弛豫。更大的放松，表明更快的镉跳跃率，观察到在重稀土元素的组合物更缺乏铟，预计将在亚晶格上的空位介导的扩散。另一方面，观察到更大的弛豫轻稀土（R = La，Ce和Pr）与过量铟的组合物，这表明镉扩散介导有一个不同的机制。在这项工作中，进行了计算机模拟，以更好地了解轻稀土所观察到的弛豫的性质以及整个稀土系列行为变化的起源。作为第一步，使用密度泛函理论（DFT）计算的系列端元LaIn 3和LuIn 3的本征缺陷的形成周期。发现这两种化合物都表现出肖特基热无序。另外的DFT模拟表明，In和R-空位之间的结合焓在LaIn 3中比在LuIn 3中大，这表明在LaIn 3中的扩散可能是由双空位介导的。还计算了Cd的位密度，发现Cd在两个端元相中占据In亚晶格比R亚晶格在能量上更有利。
In previous work, perturbed angular correlation spectroscopy (PAC) was used to determine jump rates of 111Cd, the daughter of the 111In radiotracer, in the series of phases RIn3 (R = rare-earth element) through nuclear quadrupole relaxation. Greater relaxation, indicating faster Cd jump rates, was observed in heavy rare-earths for compositions more deficient in indium, as would be expected for diffusion mediated by vacancies on the In sublattice. On the other hand, greater relaxation was observed for light rare-earths (R = La, Ce, and Pr) for compositions with excess indium, suggesting Cd diffusion is mediated there by a different mechanism. In this work, computer simulations were carried out to better understand the nature of the relaxation observed for the light rare-earths and the origin of the change in behavior across the rare-earth series. As a first step, formation enthalpies of intrinsic defects were calculated using density functional theory (DFT) for series end-members LaIn3 and LuIn3. Both compounds were found to exhibit Schottky thermal disorder. Additional DFT simulations show that the binding enthalpy between In-and R-vacancies is larger in LaIn3 than in LuIn3, suggesting that diffusion in LaIn3 might be mediated by divacancies. Site enthalpies of Cd also were calculated, and it was found more favorable energetically for Cd to occupy the In sublattice than the R sublattice in both end-member phases.