Crystal Structure of NH₃CH₂COOHH₂PO₃in the Ferroelectric Phase

Abstract

X-ray investigation was carried out to examine the ferroelectric phase transition in glycinium phosphite, NH 3 CH 2 COOHH 2 PO 3 , from the structural point of view. The result indicates that the crystal belongs to the space group P 2 1 in the ferroelectric phase and the unit cell parameters obtained at 198 K are a =9.758(2) Å, b =8.510(1) Å, c =7.375(1) Å and β=100.47(1)°. The crystal structure in ferroelectric phase was determined using an automatic four-circle diffractometer and refined to R =0.032 and R w =0.023 for 2685 independent reflections. Structure analysis clarified that in the ferroelectric phase, the hydrogen atoms between neighboring phosphite tetrahedra are in the ordered state and phosphite tetrahedra deform from those in the paraelectric phase.