Abstract: | Crystal Structure Determination of Ammonium catena-Polyphosphate II by X-Ray Powder Techniques The first structure determination of one of the five modifications of ammonium-catena-polyphosphate was performed using X-ray powder diffraction data. (NH4PO3)nII is formed by phase transformation of (NH4PO3)nI which on its part is obtained by condensation of NH4H2PO4 at 200°C in presence of urea. Modification II crystallizes in P212121 (a = 1 207.9(1), b = 648.87(8), c = 426.20(4) pm; Z = 4; 291 observed reflections; R(p) = 0.089; R(wp) = 0.111; R(I, hkl) = 0.088). The chain-anion runs parallel to the shortest axis, the period of identity is two. The ammonium ion is surrounded by a distorted tetrahedron of oxygen atoms (N? O-distances range from 285 to 292 pm, hydrogen bonds of middle strength). |