Thermal and charge transport characteristics and fine details of the crystal structure in dodecaborides LuNB12 (N = 10, 11, nat) with the Jahn-Teller instability

Structure differences of isotopically different dodecaborides LuNB12 (N = 10, 11, natural) and their impact on thermal and charge transport characteristics of the crystals have been first discovered. Atomic displacement parameters (ADPs) of Lu and B atoms are described in terms of the Einstein and D...

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Published inarXiv.org
Main Authors Bolotina, Nadezhda B, Dudka, Alexander P, Khrykina, Olga N, Glushkov, Vladimir V, Azarevich, Andrey N, Krasnorussky, Vladimir N, Gabani, Slavomir, Natalya Yu Shitsevalova, Dukhnenko, A V, Filipov, Volodymyr B, Sluchanko, Nikolay E
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 15.11.2018
Subjects
Anomalies
Charge transport
Crystal defects
Crystal structure
Crystallography
Crystals
Electron density
Isotope composition
Jahn-Teller effect
Specific heat
Structural stability
Temperature dependence
Transport properties
Unit cell
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Summary:Structure differences of isotopically different dodecaborides LuNB12 (N = 10, 11, natural) and their impact on thermal and charge transport characteristics of the crystals have been first discovered. Atomic displacement parameters (ADPs) of Lu and B atoms are described in terms of the Einstein and Debye models, respectively. Characteristic Einstein and Debye temperatures are calculated directly from the x-ray data and corresponding ADPs are separated into temperature dependent and temperature independent components. The first component is a measure of thermal atomic vibrations whereas the second one is a sum of zero vibrations and static shifts of some atoms from their crystallographic positions. Such a local disordering is more expressed in LunatB12 with 10B : 11B = 1 : 4 judging both from the large static ADP components and the Schottky anomalies in the heat capacity. Crystal structures are refined in Fm3-m group but certain distortions of the ideal cubic unit-cell values are observed in all three crystals under study due to cooperative Jahn-Teller effect. The distortions are mainly trigonal or mainly tetragonal depending on the isotope composition. Low symmetry distribution of electron density reveals itself in LunatB12 in the form of the dynamic charge stripes oriented in selected directions close to some of . The large static ADP components of LunatB12 are surprisingly combined with high conductivity of the crystal. One may suppose the static shifts (defects) are centers of pinning facilitating formation of additional conductive channels.
ISSN:2331-8422