AN X-RAY AND NEUTRON POWDER DIFFRACTION STUDY OF A NEW POLYMORPHIC PHASE OF COPPER HYDROXIDE NITRATE

High-temperature sequential powder diffractometry has revealed a phase transformation in monoclinic copper hydroxide nitrate CU2(OH)3(NO3) occurring at 158-degrees-C. It is connected with a small endothermic effect of 0.5 KJ mole-1. The high-temperature Phase is monoclinic with the unit cell dimensions a = 5.6132(7), b = 6.0986(8), c = 6.9560(9) angstrom, and beta = 92.35(1)-degrees; the space group is P2(1) with Z = 2. The crystal structure of this new phase has been determined from X-ray and neutron powder diffraction data collected at 160-degrees-C. The structure is built from wavy layers of brucite type, linked together by hydrogen bonds, as in the room-temperature phase. The main differences between the two phases are a slight reorientation of the nitrate group and some changes occurring in hydrogen bonds. (C) 1994 Academic Press, Inc.