Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study.

Choudhury, R. R.; Chitra, R.; Aliouane, N.; Schefer, J.

Protonated crystals of glycine silver nitrate (C4H10Ag2N4O10) undergo a displacive kind of structural phase transition to a ferroelectric phase at 218 K. Glycine silver nitrate (GSN) is a light-sensitive crystal. Single-crystal X-ray diffraction investigations are difficult to perform on these crystals due to the problem of crystal deterioration on prolonged exposure to X-rays. To circumvent this problem, single-crystal neutron diffraction investigations were performed. We report here the crystal structure of GSN in a ferroelectric phase. The final R value for the refined structure at 150 K is 0.059. A comparison of the low-temperature structure with the room-temperature structure throws some light on the mechanism of the structural phase change in this crystal. We have attempted to explain the structural transition in GSN within the framework of the vibronic theory of ferroelectricity, suggesting that the second-order Jahn-Teller (pseudo-Jahn-Teller) behavior of the Ag ion in GSN leads to structural distortion at low temperature (218 K).

SILVER nitrate; NEUTRON diffraction crystallography; X-ray diffraction; FERROELECTRIC crystals; JAHN-Teller effect

Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2013, Vol 69, Issue 6, p595

2052-5192

Academic Journal

10.1107/S2052519213024573