Preparation and structural determination of the high-temperature form of potassium dihydrogen phosphate

Crystals of the high-temperature form of potassium dihydrogen phosphate (KH 2PO4 (KDP)) have been prepared by a hydrothermal method. The old parameters and space group are rectified and the structure is solved for the first ti me. It crystallizes in the monoclinic system, space group P2(1)/c (No. 14), a = 7.4514(7) Angstrom, b=14.5582(9) Angstrom, c=9.366(7) Angstrom, and be ta 127.65(1)degrees, and Z=8, The structure is refined to R = 0.032 for 153 0 independent reflections and compared with the other KDP forms, The distri bution of hydrogen atoms over PO4 tetrahedra and the structural relationshi p with the various forms of KDP are discussed. The doubling of the b parame ter is related to structural features. (C) 1998 Academic Press.