2017/08/31 by Ruoxi Yang, Ruo Xi Yang, Jonathan M. Skelton +4 · 250 citations
Chemistry · Engineering · Materials Science · Physics and Astronomy · #Anharmonicity #Caesium #Chemistry #Condensed matter physics #Crystal structure #Crystallography #Halide #Inorganic chemistry #Lattice (music) #Materials science #Octahedron #Optical properties and cooling technologies in crystalline materials #Perovskite (structure) #Perovskite Materials and Applications #Phonon #Physics #Solid-state spectroscopy and crystallography #cond-mat.mtrl-sci
paper · pdf · doi:10.1021/acs.jpclett.7b02423
published in The Journal of Physical Chemistry Letters 8(19), 4720-4726 (American Chemical Society)
arxiv created 2017/09/14 · openalex publication_date 2017/09/14 · arxiv updated 2017/10/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The local crystal structures of many perovskite-structured materials deviate from the average space-group symmetry. We demonstrate, from lattice-dynamics calculations based on quantum chemical force constants, that all of the cesium-lead and cesium-tin halide perovskites exhibit vibrational instabilities associated with octahedral titling in their high-temperature cubic phase. Anharmonic double-well potentials are found for zone-boundary phonon modes in all compounds with barriers ranging from 108 to 512 meV. The well depth is correlated with the tolerance factor and the chemistry of the composition, but is not proportional to the imaginary harmonic phonon frequency. We provide quantitative insights into the thermodynamic driving forces and distinguish between dynamic and static disorder based on the potential-energy landscape. A positive band gap deformation (spectral blue shift) accompanies the structural distortion, with implications for understanding the performance of these materials in applications areas including solar cells and light-emitting diodes.