On the mechanism of I – II phase transition of DSP

Abstract A brief review is given on the studies of the I – II phase transition mechanism of Ca2Sr(C2H5CO2)6 (DSP), by comparison with the deuterated compounds Ca2Sr(C2D5CO2)6 (DDSP), with an emphasis on the role of the motion of the propionate molecules. The deuteration of all hydrogen sites increases the moment of inertia of the molecule without any change in its geometrical structure and also in the environmental potential around the molecule. The X-ray diffraction study of DDSP confirms that the deuterated propionate molecule have the same structure as that of the nondeuterated one. Dielectric, optical, light scattering and neutron scattering experiments of DDSP reveal a dynamical mechanism of the phase transition. A minor role of the hindered rotational motion of the propionate molecule in the mechanism is concluded in contrast to thetrigger mechanism suggested previously.

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