Laser Raman study of the low-temperature phase transformation in [N(CH3)4]2CuCl4 single crystals |
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| Affiliation: | 1. Laboratory of Multifunctional Materials and Applications (LMMA), University of Sfax, Faculty of Sciences of Sfax (FSS), Street Soukra km 3.5 BP 1171, 3000 Sfax, Tunisia;2. Laboratory of Physics of Condensed Matter (LPMC), University of Picardie Jules Verne, Scientific Pole, 33 rue Saint-Leu, 80039 Amiens Cedex 1, France;3. Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia;1. Samara State Technical University, 244 Molodogvardeiskaya st., Samara 443100, Russia;2. Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille, France;3. Institut Chevreul, University of Lille & CNRS, Villeneuve dAscq F-59655, France;4. All-Russian Research Institute of Oil Refining, 6/1 Aviamotornaya st., Moscow 111116, Russia;1. IFP Energies Nouvelles, Rond-point de l’échangeur de Solaize, BP 3 69360 Solaize, France;2. Dipartimento di Chimica NIS Centre and INSTM – Centro di Riferimento, Università di Torino, Via Quarello 15 Torino, I-10135, Italy;1. Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, PR China;2. State Key Laboratory of Heavy Oil Processing, Key Laboratory of Catalysis of China National Petroleum Corporation (CNPC), China University of Petroleum (East China), Qingdao, 266580, PR China |
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| Abstract: | The results of a detailed temperature-dependent Raman study of single crystals of [N(CH3)4]2CuCl4 are reported in different spectral regions. The observed splittings of the symmetric stretching modes of the N(CH3)+4 ion below 250 K and the CuCl2−4 ion below 50 K into doublets have been explained as being due to the presence of ions on two energetically inequivalent positions within the lattice. From a temperature dependence of the half-widths, frequency separation, relative intensities of the two components of the CN stretch and other thermosensitive spectral changes, we have discovered a new first order type phase transition in this system at ∼50 K due to ordering of ions from one configuration to another. The reordering in phase IV up to 50 K takes place via continuous movement of cations from the disordered to ordered configuration, but below 50 K the ions freeze in the two inequivalent configurations. The dynamics of ordering of the ions at different temperatures is discussed in this communication. |
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