Correct identification of local configurations of dopants and point defects in random alloys poses a challenge to both computational modeling and experimental characterization methods. In this paper, we propose and implement a computationally efficient approach to address this problem. Combining special quasirandom structures, virtual crystal approximation, and real-space lattice static Green’s functions, we are able to calculate, at moderate computational cost, the local phonon density of states (LPDOSs) of impurities in a random alloy crystal for system sizes, surpassing the capabilities of a conventional, cubic-scaling, density functional theory. We validate this method by showing that our LPDOS predictions of substitutional silicon in GaAs and InAs are in excellent agreement with the experimental data. For the case study, we investigate a variety of local configurations of Si and Se substitutional dopants and cation vacancies in quasirandom In 0.5 Ga 0.5 As alloys. In all cases, the impurity LPDOS in a random alloy exhibits qualitatively different signatures from those in the pure binary compounds GaAs and InAs. Specifically, they are characterized by a wide continuous band (rather than narrow discrete peaks) of vibrational modes at frequencies typically higher than the bulk modes, a sign of coupling between localized vibrations of the impurity and those of its random neighboring host atoms. The accuracy and computational cost of this approach open a way to the simulation of impurities in random structures on a large scale and the prediction of vibrational signatures of alloys with defects.

中文翻译：

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对完全随机合金中掺杂剂和缺陷的振动特征进行指纹识别：对 In0.5Ga0.5As 中 Si、Se 和空位的从头算例研究

正确识别随机合金中掺杂剂和点缺陷的局部配置对计算建模和实验表征方法提出了挑战。在本文中，我们提出并实施了一种计算高效的方法来解决这个问题。结合特殊的准随机结构、虚拟晶体近似和实空间晶格静态格林函数，我们能够以适中的计算成本计算系统尺寸的随机合金晶体中杂质的局部声子态密度 (LPDOS)，超过传统的三次标度密度泛函理论的能力。我们通过展示我们对 GaAs 和 InAs 中替代硅的 LPDOS 预测与实验数据非常一致来验证这种方法。对于案例研究，我们研究了准随机 In 0.5 Ga 0.5 As 合金中 Si 和 Se 置换掺杂剂和阳离子空位的各种局部配置。在所有情况下，随机合金中的杂质 LPDOS 表现出与纯二元化合物 GaAs 和 InAs 在性质上不同的特征。具体而言，它们的特征在于振动模式的宽连续带（而不是窄的离散峰），频率通常高于体模式，这是杂质的局部振动与其随机相邻主体原子的局部振动之间耦合的标志。这种方法的准确性和计算成本为大规模模拟随机结构中的杂质和预测具有缺陷的合金的振动特征开辟了道路。