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End date: 2024 × Start date: 2020 × End date: 2024 × Start date: 2020 × Publisher: Weinheim : Wiley-VCH × Subject: crystal structure × WGL Institute: IFWD ×

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    Amorphous-Like Ultralow Thermal Transport in Crystalline Argyrodite Cu7PS6
    (Weinheim : Wiley-VCH, 2024) Shen, Xingchen; Ouyang, Niuchang; Huang, Yuling; Tung, Yung‐Hsiang; Yang, Chun‐Chuen; Faizan, Muhammad; Perez, Nicolas; He, Ran; Sotnikov, Andrei; Willa, Kristin; Wang, Chen; Chen, Yue; Guilmeau, Emmanuel
    Due to their amorphous-like ultralow lattice thermal conductivity both below and above the superionic phase transition, crystalline Cu- and Ag-based superionic argyrodites have garnered widespread attention as promising thermoelectric materials. However, despite their intriguing properties, quantifying their lattice thermal conductivities and a comprehensive understanding of the microscopic dynamics that drive these extraordinary properties are still lacking. Here, an integrated experimental and theoretical approach is adopted to reveal the presence of Cu-dominated low-energy optical phonons in the Cu-based argyrodite Cu7PS6. These phonons yield strong acoustic-optical phonon scattering through avoided crossing, enabling ultralow lattice thermal conductivity. The Unified Theory of thermal transport is employed to analyze heat conduction and successfully reproduce the experimental amorphous-like ultralow lattice thermal conductivities, ranging from 0.43 to 0.58 W m−1 K−1, in the temperature range of 100–400 K. The study reveals that the amorphous-like ultralow thermal conductivity of Cu7PS6 stems from a significantly dominant wave-like conduction mechanism. Moreover, the simulations elucidate the wave-like thermal transport mainly results from the contribution of Cu-associated low-energy overlapping optical phonons. This study highlights the crucial role of low-energy and overlapping optical modes in facilitating amorphous-like ultralow thermal transport, providing a thorough understanding of the underlying complex dynamics of argyrodites.
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    The Weak 3D Topological Insulator Bi12Rh3Sn3I9
    (Weinheim : Wiley-VCH, 2020) Lê Anh, Mai; Kaiser, Martin; Ghimire, Madhav Prasad; Richter, Manuel; Koepernik, Klaus; Gruschwitz, Markus; Tegenkamp, Christoph; Doert, Thomas; Ruck, Michael
    Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation-free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well-characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth-based subiodides and recently succeeded in synthesizing a new compound Bi12Rh3Sn3I9, which is structurally closely related to Bi14Rh3I9 – a stable, layered material. In fact, Bi14Rh3I9 is the first experimentally supported weak 3D TI. Both structures are composed of well-defined intermetallic layers of ∞2[(Bi4Rh)3I]2+ with topologically protected electronic edge-states. The fundamental difference between Bi14Rh3I9 and Bi12Rh3Sn3I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14Rh3I9 are isolated by ∞1[Bi2I8]2− chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞2[Sn3I8]2− layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity. © 2020 The Authors. Published by Wiley-VCH GmbH
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    Syntheses and Molecular Structures of Liquid Pyrophoric Hydridosilanes
    (Weinheim : Wiley-VCH, 2020) Gerwig, Maik; Böhme, Uwe; Friebel, Mike; Gründler, Franziska; Franze, Georg; Rosenkranz, Marco; Schmidt, Horst; Kroke, Edwin
    Trisilane, isotetrasilane, neopentasilane, and cyclohexasilane have been prepared in gram scale. In-situ cryo crystallization of these pyrophoric liquids in sealed capillaries on the diffractometer allows access to the single crystal structures of these compounds. Structural parameters are discussed and compared to gas-phase electron diffraction structures from literature and with the results from quantum chemical calculations. Significantly higher packing indices are found for the silanes compared to the corresponding alkanes. Radiation with ultraviolet light (365 nm) and parallel ESR (EPR) measurement shows that cyclohexasilane is easily split into radicals, which subsequently leads to the formation of branched and chain-like oligomers. The other compounds form no radicals under these conditions. NMR spectra of all four compounds have been recorded. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.