Structural phase transition in ferroelectric glycine silver nitrate

The structural investigation of the ferroelectric phase transition in glycine silver nitrate has revealed that the transition at T c = 218 K is due to the displacement of the Ag+ ions from the plane made by the carboxyl oxygens of glycine zwitterions coordinated to it. Since the transition takes place between two ordered structures the thermal anomaly at T c is very weak, the transition enthalpy and transition entropy were found to be Δ H = 6.6 J / mol and the transition entropy Δ S = 0.03 J K − 1 mol − 1 respectively. These crystals are held together by a network of hydrogen bonds. In order to study these interactions the Raman spectrum of GSN was recorded and discussed in the light of ferroelectricity in glycine complexes in general.