Hadjiev V G, Wang C, Wang Y, Su X, Calderon H A, Robles Hernandez F, Wang Z M, Bao J M
Texas Center for Superconductivity, University of Houston, Houston, TX 77204, United States of America. Department of Mechanical Engineering, University of Houston, Houston, TX 77204, United States of America.
J Phys Condens Matter. 2018 Oct 10;30(40):405703. doi: 10.1088/1361-648X/aadeb4. Epub 2018 Sep 4.
CsPbBr is a stable, water-resistant, material derived from CsPbBr perovskite and featuring two-dimensional Pb-Br framework separated by Cs layers. Both compounds can coexist at nanolength scale, which often produces conflicting optical spectroscopy results. We present a complete set of polarized Raman spectra of nonluminescent CsPbBr single crystals that reveals the symmetry and frequency of nondegenerate Raman active phonons accessible from the basal (0 0 1) plane. The experimental results are in good agreement with density functional perturbation theory simulations, which suggests that the calculated frequencies of yet unobserved double degenerate Raman and infrared phonons are also reliable. Unlike CsPbBr, the lattice dynamics of CsPbBr is stable as evidenced by the calculated phonon dispersion. The sharp Raman lines and lack of a dynamic-disorder-induced central peak in the spectra at room temperature indicate that the coupling of Cs anharmonic motion to Br atoms, known to cause the dynamic disorder in CsPbBr, is absent in CsPbBr.
CsPbBr是一种稳定、防水的材料，由CsPbBr钙钛矿衍生而来，具有由Cs层分隔的二维Pb-Br框架。这两种化合物可以在纳米尺度上共存，这常常产生相互矛盾的光谱学结果。我们展示了非发光CsPbBr单晶的一整套偏振拉曼光谱，揭示了从基面（0 0 1）平面可获得的非简并拉曼活性声子的对称性和频率。实验结果与密度泛函微扰理论模拟结果高度吻合，这表明计算出的尚未观测到的双重简并拉曼声子和红外声子的频率也是可靠的。与CsPbBr不同，CsPbBr的晶格动力学是稳定的，这由计算出的声子色散所证明。室温下光谱中尖锐的拉曼线以及缺乏动态无序诱导的中心峰表明，已知会导致CsPbBr中动态无序的Cs非谐运动与Br原子的耦合在CsPbBr中不存在。
