REDETERMINATION OF THE CRYSTAL-STRUCTURE OF PARAELECTRIC DIGLYCINE NITRATE .1. CRYSTAL-STRUCTURE AT 220 K AND 293 K

The crystal structure of diglycine nitrate (NH2COOH)(2)HNO3 (DGN) has been redetermined in the paraelectric phase at two temperatures: 293 K and 220 K. Paraelectric DGN is monoclinic, at 293 K a = 9.4602(10) An gstrom, b = 5.1728(5) Angstrom, c = 9.2241(10) Angstrom and beta = 97. 217(15)degrees, at 220 K a = 9.4647(10) Angstrom, b = 5.1659(5) Angstr om, c = 9.1583(10) Angstrom and beta = 97.530(15)degrees. Paraelectric phase of DGN is heavily disordered with a space group of the averaged crystal structure P2(1)/a. As compared to the earlier results, additi onal disorder has been found in the case of NO3- anions, which occupy at random four different orientations with occupancy factors depending on temperature.