A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain the low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.
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http://dx.doi.org/10.1038/ncomms7723 | DOI Listing |
Nat Nanotechnol
December 2024
Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
Due to quasi-one-dimensional confinement, nanowires possess unique electronic properties, which can promote specific device architectures. However, nanowire growth presents paramount challenges, limiting the accessible crystal structures and elemental compositions. Here we demonstrate solid-state topotactic exchange that converts wurtzite InAs nanowires into Zintl EuInAs.
View Article and Find Full Text PDFInorg Chem
July 2024
Department of Chemistry, Clemson University, Clemson, South Carolina 29634-0973, United States.
Three novel nickel-phosphate structures are reported, Ni(PO)(OH) (), Ni(PO)(HPO)(OH) (), and NaNiPO (). Each new system was prepared via a high-temperature hydrothermal synthesis at 600-650 °C. All three compounds are built of quasi-one-dimensional (quasi-1-D) Ni containing chains with varying phosphate bridging modes and were characterized by single crystal X-ray diffraction and magnetic susceptibility.
View Article and Find Full Text PDFPhys Chem Chem Phys
December 2021
Department of Physics, National Technical University of Athens, Heroon Polytechniou 9 Zographou Campus, 15780, Athens, Greece.
Topotactic transformations of suitable layered three-dimensional precursors are among the most robust methods to prepare two-dimensional (2D) materials based on silicon or germanium. Here we use Density Functional Theory calculations to probe the mechanisms underlying the formation of 2D-Si sheets functionalized with iodine atoms (SiI) or acetonitrile molecules [Si(MeCN)] starting from a layered CaSi precursor. We identify the sequence of exothermic surface reactions that enable the adsorption of, not only iodine atoms, but, surprisingly, also of solvent acetonitrile molecules on both sides of the top layer of a Si-terminated CaSi surface and its ensuing exfoliation as a standalone 2D sheet.
View Article and Find Full Text PDFNat Commun
April 2015
1] Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA [2] Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals.
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