Low temperature powder diffraction and DFT solid state computational study of hydrogen bonding in NH4VO3

The crystal structure of NH4VO3 was refined by the geometry optimization done by total energy minimization in solid state using DFT/plane waves approach. The lattice parameters were derived by the Le Bail technique from the low temperature X-ray (40-293 K) and synchrotron (100-293 K) powder diffraction data. The structure is formed by the infinite chains of irregular VO4 tetrahedra running approximately parallel to the c-axis, which are interlinked by the ammonium ions placed between them. The ammonium ions link to the[VO4]∞ chains through one linear, one bifurcated and two trifurcated N-H...O hydrogen bonds. Considering their stability there are six distinct N-H...O hydrogen bonds: two strong with the N-H...O bond angles close to the straight, two medium with the bond angles of 123 and 148 and two very bent (105 and 107 ) and hence weak hydrogen bonds. There is a reasonable agreement between the energies of the stretching ν(NH) modes estimated using the optimised N...O contact distances and those obtained experimentally. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)