Molecular dynamics in triglycine sulphate by cold neutron spectroscopy |
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Authors: | V Tripadus A Radulescu J Pieper A Buchsteiner A Podlesnyak S Janssen A Serban |
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Institution: | 1. National Institute of Physics and Nuclear Engineering, 76900 Bucharest, Romania;2. Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany;3. Berlin Neutron Scattering Center, Hahn-Meitner-Institut, 14109 Berlin, Germany;4. Laboratory for Neutron Scattering, Paul Scherrer Institute, 5232 Villigen, Switzerland |
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Abstract: | Molecular dynamics of the ferroelectric compound triglycine sulphate (TGS) was studied by quasi-elastic neutron scattering. From among the three glycine molecules forming the unit cell the non-planar GI molecule is responsible for the polarisation which occurs in crystal and for the order–disorder ferroelectric phase transition at Tc = 49 °C. This molecule also shows a complex dynamics much faster than that performed by the other glycine molecules. The key group of this molecule is the amino group that, on one hand, seems to be responsible for the phase transition and, on the other hand, performs motional processes spread on a wide time scale. These motions have been detailed studied by means of different energy resolution windows within the quasi-elastic scattering range. We found that the dynamics of this group develops in a restricted spatial volume and consists in a faster rotational diffusion around the molecular axis of the group and a slower flipping dynamics between two symmetrical positions on both sides of a mirror plane containing the molecular axis of GI molecule. |
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Keywords: | Neutron scattering Ferroelectrics Dynamics in restricted volumes |
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