Investigating short-range order in triglycine sulphate using x-ray and neutron diffuse scattering

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Date
2012-02-02
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Australian Institute of Physics
Abstract
Triglycine sulphate (TGS) [(NH2CH2COOH)3H2SO4] is a hydrogen-bonded ferroelectric with a phase transition temperature of 322K [1]. The phase transition is reversible and second order, order disorder type, making TGS of fundamental interest in the field of phase transitions [2]. Above the critical temperature, one of the glycine molecules is disordered across a mirror plane. Below the critical temperature, it chooses a side, breaking the symmetry. The ferroelectric state is obtained through the ordering of the glycine orientations on neighbouring sites, but the mechanism for the phase transition is not well understood. We have investigated the short-range order in TGS by collecting single crystal x-ray and neutron diffuse scattering data on hydrogenous and fully deuterated TGS respectively. Data was collected at temperatures from well below to well above TC. We have also developed a model for the short-range order using the program ZMC [3]. This has given us some new insight into the behavior of the disordered glycine in TGS. For example, above TC, the orientations of the disordered glycine appear to be correlated over short range rather than being completely random as suggested by the average structure.
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Keywords
Neutron diffraction, X-ray diffraction, Hydrogen, Ferroelectric materials, Phase transformations, Order-disorder transformations, Crystal-phase transformations, Deuteration
Citation
Hudspeth, J. M., Goossens, D. J., Gutmann, M. J., Studer, A. J., & Welberry, T. R. (2012). Investigating short-range order in triglycine sulphate using x-ray and neutron diffuse scattering. Paper presented to the 36th Annual Condensed Matter and Materials Meeting, Wagga 2012, Charles Sturt University, Wagga Wagga, NSW, 31st January – 3rd February, 2012. Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2012/
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https://physics.org.au/wp-content/uploads/cmm/2012/
 https://apo.ansto.gov.au/dspace/handle/10238/12052
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