Direct Measurements of the Atomic Displacements Related to the Ferroelectric Transition in Sn₂P₂S₆

The Sn₂P₂S₆ is known to be ferroelecetric and is one of the few Sn based ferroelectric (FE) systems which have been discovered. The true nature of the onset of the electric polarization has not be previously correlated with the changes in atomic structure. We have conducted structural measurements on multiple length scales as a function of temperature. In addition the structural results are compared to the low frequency phonons obtained from Raman scattering measurements. A complete model of the polar state of this system is developed.