NMR study of molecular dynamics and phase transitions in dimethyl ammonium hexabromo selenate $[NH_2(CH_3)_2]_2SeBr_6$

Murthy, BVS and Ramesh, KP and Ramakrishna, J (2000) NMR study of molecular dynamics and phase transitions in dimethyl ammonium hexabromo selenate $[NH_2(CH_3)_2]_2SeBr_6$. In: Journal of Physics and Chemistry of Solids, 61 (6). pp. 961-968.

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Abstract

$^1H$ spin lattice relaxation study in the temperature range 439–77 K has been carried out in dimethyl ammonium (DMA) hexabromo selenate. A high temperature phase transition is observed as a dip in $T_1$ around 360 K, followed by a slope change a 222 K, and a discontinuous jump in $T_1$ at 154 K, which are also attributed to phase transitions. DMA diad axis motion and spin– rotation interaction are found to be the dominant mechanisms responsible for the observed $T_1$ behaviour above 222 K, while between 222 and 154 K, DMA torsional oscillations contribute significantly. Below 154 K the relaxation is governed by the methyl group dynamics. The motional effects are also reflected in the second moment variation with temperature.

Item Type:	Journal Article
Publication:	Journal of Physics and Chemistry of Solids
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Elsevier B.V.
Keywords:	Molecular dynamics;Dimethyl ammonium dynamics;D. Phase transitions;D. Nuclear magnetic resonance (NMR)
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	08 Aug 2008
Last Modified:	19 Sep 2010 04:48
URI:	http://eprints.iisc.ac.in/id/eprint/15490

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