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

Crystals of the high-temperature form of potassium dihydrogen phosphate (KH2PO4 (KDP)) have been prepared by a hydrothermal method. The old parameters and space group are rectified and the structure is solved for the first time. 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 beta 127.65(1)degrees, and Z=8, The structure is refined to R = 0.032 for 1530 independent reflections and compared with the other KDP forms, The distribution of hydrogen atoms over PO4 tetrahedra and the structural relationship with the various forms of KDP are discussed. The doubling of the b parameter is related to structural features. (C) 1998 Academic Press.