Structural study of ND4I at high pressures and low temperatures |
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Authors: | D P Kozlenko V P Glazkov B N Savenko V A Somenkov S Hull |
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Institution: | 1. Frank Laboratory of Neutron Physics, JINR , 141980, Dubna Moscow Reg., Russia;2. Russian Research Center “Kurchatov Institute” , 123182, Moscow, Russia;3. ISIS Facility, Rutherford Appleton Laboratory , Chilton, Didcot, Oxon OX11 OQX, UK |
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Abstract: | Abstract Structure, positional, and thermal parameters of ND4I were studied at high pressures up to 90 kbar and low temperatures down to 10 K using time-of-flight neutron diffraction. The phase transition from a disordered CsCI-type cubic phase ND4I(II) into a recently discovered high pressure phase ND4I(V) was observed at P = 80(5) kbar. Surprisingly, the structure of the high pressure phase V was found to bear a strong resemblance to that of the ambient pressure, low-temperature phase III - tetragonal structure with an antiparallel ordering of ammonium ions, space group P4/nmm. The critical value of the deuterium positional parameter corresponding to the II-V transition is close to the one for the phase transition between the disordered and ordered CsCl-type cubic phases II and IV in other ammonium halides. |
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Keywords: | Neutron diffraction High pressure Ammonium iodide Low temperature |
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