Abstract
Metal halide perovskites (MHPs) have emerged as highly promising materials for optoelectronic applications, with all-inorganic MHPs presenting enhanced stability compared to their hybrid counterparts. Here, we investigate the atomic dynamics and structural fluctuations in single crystals of CsSnBr3 and CsPbBr3 through systematic inelastic neutron scattering (INS) measurements as a function of temperature. Our experiments are compared with first-principle simulations, augmented with large-scale molecular dynamics modeling, based on machine-learned neural network potentials. Through both INS and simulations, we find quasi-elastic diffuse rods in reciprocal space in both compounds, originating from fluctuating planar domains featuring correlated tilts of Br octahedron. The diffuse rods exhibit a slow, overdamped dynamic process, modulated across Q space, reflecting the strong lattice anharmonicity of the inorganic framework. We do not find evidence for dynamic off-centering of the Sn2+ ions besides phonon vibrations at the center of the Br octahedron. These results offer valuable insights into the unusual anharmonic atomic dynamics and intricate correlated structural distortions in MHPs, which will be critical for rationalizing and further tailoring their thermal and optoelectronic properties.
| Original language | English |
|---|---|
| Article number | 065401 |
| Journal | Physical Review Materials |
| Volume | 9 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 2025 |
Funding
Neutron scattering data collection and analysis and first-principle simulations (CM, XH, HML, MKG, TL, PP, and OD) were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award No. DE-SC0019978. Work at the Materials Science Division at Argonne National Laboratory (synthesis, crystal growth, characterization, and neutron scattering measurements) was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, both DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. The beam time was allocated to CTAX on proposal number IPTS-29800. Experiments at the ISIS Neutron and Muon Source were supported by a beamtime allocation RB2310120 from the Science and Technology Facilities Council. Data is available at: . This research used resources of the National Energy Research Scientific Computing Center (NERSC), a Department of Energy Office of Science User Facility using NERSC Award BES-ERCAP0033278.