Neutron-diffraction investigation of atomic structure of crystals of NH4HSeO4 at T = 293 and 400 K

From neutron-diffraction data the authors have investigated the atomic structure of the para phase of the crystals of NH4HSeO4 at 293 and 400 K. They locate the H atoms and analyze the character of the hydrogen bonds. Comparison of the geometry of the hydrogen bonds and the thermal vibration parameters of the atoms led to the conclusion that the model of dynamic disordering of an H atom at one of the H-bonds is preferable. The nonequivalence of the H bonds is reflected in the nonequivalence of the [SeO4] tetrahedra