Solid-State NMR Studies of Two Phases for Tin Hexathiohypodiphosphate

Magic-angle spinning ³¹P and ¹¹⁹Sn NMR spectra of Sn₂P₂S₆ are presented. Spectra were recorded at room temperature, 80 °C, and 100 °C. Two distinct center-band resonances are observed both for the phosphorus and for the tin spectra at room temperature. When the temperature is raised above the ferroelectric phase-transition temperature (T_c ∼ 70 °C), both phosphorus and tin show single center-band resonances. These results are generally consistent with earlier structural characterization. The spinning sideband patterns at both low and high temperatures were analyzed in order to determine the principal components of the shielding tensor. Consideration of the ³¹P shielding tensor suggests that the point symmetry at the phosphorus site in the room-temperature phase is less than that implied by X-ray analysis.