AI 中文总结
本研究提出一种利用中等尺寸超胞信息结合布里渊区采样的方法，可高效获取缺陷处的稀极限原子位移，应用于金刚石NV色心和硅T中心，为解决缺陷稀极限跃迁问题提供关键支撑。
AI 中文摘要
缺陷及其与半导体宿主晶格的相互作用在多种技术中发挥着关键作用。当缺陷在两个电子态之间跃迁时，晶格会发生相应畸变，缺陷附近会出现大位移，进而诱导相邻原子产生位移，如此传递后，距缺陷数百埃的原子也会产生微小位移。由于超胞尺寸有限，第一性原理计算难以准确描述这些位移。本文展示了一种利用典型中等尺寸超胞信息高效获取稀极限原子位移的方法：首先在小超胞中获取原子位移，并将其转换为简谐势能面下的力差；随后将该力差与不同q点的声子模式展开到Born-von Kármán超胞中，得到稀极限原子位移。我们关键分析了力差的收敛行为，并研究了产生这些力的可能电子密度差，证明中等尺寸超胞足以处理内部跃迁和束缚激子跃迁。本文给出了该方法的两个应用示例：（1）计算金刚石中NV色心和硅中T中心的发光光谱；（2）获取这些缺陷的稀极限构型坐标图。特别地，我们发现与声学声子模式的耦合会降低构型坐标图中的受主模式频率。本研究为解决缺陷处真正稀极限跃迁问题提供了必要的缺失要素。
英文摘要
Defects and their interaction with the semiconductor host lattice play an essential role in a variety of technologies. When a defect transitions between two electronic states, the lattice distorts in response. Large displacements occur near the defect, inducing displacements on neighboring atoms, and so on, producing small displacements on atoms hundreds of Ångströms from the defect. Describing these displacements accurately is challenging for first-principles calculations due to limited supercell sizes. Here we demonstrate a procedure to efficiently obtain dilute-limit atomic displacements, using information obtained in typical modest supercells. In our approach, the atomic displacements are first obtained in a small supercell and converted into a force difference under a harmonic potential energy surface. The force difference and phonon modes at different ${\bf q}$-points are then unfolded into the Born-von Kármán supercell to obtain the dilute-limit atomic displacements. We critically analyze the convergence behavior of the force difference and study possible electron density differences that give rise to those forces, arguing that modest supercells are sufficient for internal transitions and bound-exciton transitions. Two example applications of our approach are given: (1) we calculate the luminescence spectrum of the NV center in diamond and the T center in Si and (2) we obtain dilute-limit configuration coordinate diagrams for these defects. In particular, we find that coupling to acoustic phonon modes reduces the accepting-mode frequency in the configuration coordinate diagram. Our work provides the missing ingredients necessary to address truly dilute-limit transitions at defects.
