Neutron diffraction study of MgNH4PO4.6H2O (struvite) and survey of water molecules donating short hydrogen bonds

MgNH4PO4.6H20 (struvite), Mr=245'4, Pmn2, a=6.955(1), b=6.142(1), c=11.218(2)A, V= 479.2 (2) ]k 3, Z = 2, Dx = 1.70 Mg m -3, neutrons, A 1.179/~, /z = 0.03 mm -t, room temperature. The structure was refined from 685 unique neutron diffraction data to R -- 0.032. The ammonium group is completely ordered and linked by one single and several polyfurcated N...O hydrogen bonds varying from 2.800 (5) to 3498 (5) ~. Six out of eight W...O hydrogen bonds donated by the water molecules are in the range 2.630 (4)-2.649 (5) A. A survey of hydrogen bonds studied by neutron diffraction reveals, on