Pulsed Nitrogen—Proton Double Resonance Study of the Ferroelectric Transition in Triglycine Sulfate

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Abstract
The technique of nuclear magnetic pulsed double resonance in the rotating frame has been used to study the changes in the 14N quadrupole interactions in a triglycine sulfate (TGS) single crystal on going from the paraelectric to the ferroelectric phase. The 14N electric field gradient tensors have been determined above as well as below Tc. The most significant effect of the ferroelectric transition is a large change in the time averaged value of the C–N bond direction of glycine I and the onset of chemical nonequivalence of glycines II and III due to an ordering of the protons in the short O–H ··· O bond. The results show that the phase transition in TGS is of the order—disorder type as far as the glycine groups are concerned.