Structural phase transition in elpasolite-like (NH4)2KWO3F3 |
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Authors: | I N Flerov M V Gorev V D Fokina A F Bovina M S Molokeev Yu V Boĭko V N Voronov A G Kocharova |
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Institution: | (1) Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia |
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Abstract: | A new chemical compound, (NH4)2KWO3F3, was synthesized. The Rietveld-refined crystal structure was found to be cubic at room temperature and to belong to the elpasolite
family (space group
). The heat capacity and unit cell parameters were studied within a broad temperature range. A second-order phase transition
was found to occur at 235.4 K and to be well described in terms of phenomenological theory. Hydrostatic pressure broadens
the temperature interval of stability of the cubic phase (dT0/dp = −10.8 K GPa−1). A possible model of structural ordering based on a comparison of the entropy parameters and electron density distribution
in oxygen and fluorine atoms is discussed. |
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Keywords: | |
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