biostudies-literatureAcharyya PDST | Science and Engineering Research Board (SERB)Department of Science and Technology, Ministry of Science and Technology (DST)5053https://www.ebi.ac.uk/biostudies/studies/S-EPMC9420152biostudies-literatureUnknown13(1)As the periodic atomic arrangement of a crystal is made to a disorder or glassy-amorphous system by destroying the long-range order, lattice thermal conductivity, κ_L, decreases, and its fundamental characteristics changes. The realization of ultralow and unusual glass-like κ_L in a crystalline material is challenging but crucial to many applications like thermoelectrics and thermal barrier coatings. Herein, we demonstrate an ultralow (~0.20 W/m·K at room temperature) and glass-like temperature dependence (2-400 K) of κ_L in a single crystal of layered halide perovskite, Cs₃Bi₂I₆Cl₃. Acoustic phonons with low cut-off frequency (20 cm^-1) are responsible for the low sound velocity in Cs₃Bi₂I₆Cl₃ and make the structure elastically soft. While a strong anharmonicity originates from the low energy and localized rattling-like vibration of Cs atoms, synchrotron X-ray pair-distribution function evidence a local structural distortion in the Bi-halide octahedra and Cl vacancy. The hierarchical chemical bonding and soft vibrations from selective sublattice leading to low κ_L is intriguing from lattice dynamical perspective as well as have potential applications.Nature communicationsGlassy thermal conductivity in Cs₃Bi₂I₆Cl₃ single crystal.PMC9420152CRG/2018/002197DST/SJF/CSA-02/2018-19SB/SJF/2019-20/06Ghosh TPal KAcharyya PSwain DRana KSSoni ADutta MBiswas KEtter MWaghmare UVfalseGlassy thermal conductivity in Cs₃Bi₂I₆Cl₃ single crystal.As the periodic atomic arrangement of a crystal is made to a disorder or glassy-amorphous system by destroying the long-range order, lattice thermal conductivity, κ_L, decreases, and its fundamental characteristics changes. The realization of ultralow and unusual glass-like κ_L in a crystalline material is challenging but crucial to many applications like thermoelectrics and thermal barrier coatings. Herein, we demonstrate an ultralow (~0.20 W/m·K at room temperature) and glass-like temperature dependence (2-400 K) of κ_L in a single crystal of layered halide perovskite, Cs₃Bi₂I₆Cl₃. Acoustic phonons with low cut-off frequency (20 cm^-1) are responsible for the low sound velocity in Cs₃Bi₂I₆Cl₃ and make the structure elastically soft. While a strong anharmonicity originates from the low energy and localized rattling-like vibration of Cs atoms, synchrotron X-ray pair-distribution function evidence a local structural distortion in the Bi-halide octahedra and Cl vacancy. The hierarchical chemical bonding and soft vibrations from selective sublattice leading to low κ_L is intriguing from lattice dynamical perspective as well as have potential applications.2022-01-01T00:00:00Z2022 Aug2025-04-18T19:06:51.397Z2025-04-07T06:48:14.587ZS-EPMC94201523603022410.1038/s41467-022-32773-4