The hydrogen positions in bayerit, Al(OH)3

With Al(OD)3 powder at room temperature and at 4 K, a neutron diffraction measurement was carried out, which served for the determination of hydrogen positions and for a refinement of the whole structure. A reliability factor R = 6.2% was obtained for room temperature and with one isotropic temperature factor for each element. Compared to earlier statements, the lattice constant c had to be doubled, and the space group had to be redefined as P21/n-instead of P21/a. The additional reflexions substantiating these new specifications can be observed in the neutron diagram, but not in the X-ray diagram. In accordance with this, the AlO3 arrangement fits approximately to the former specifications of crystal symmetry, to which, in a pure geometrical sense, the hydrogen arrangement is in fundamental contrast. Among the six symmetrically independent hydrogen atoms, three are located in weak hydrogen bonds within the same oxygen layer, the other ones form hydrogen bonds of medium strength between adjacent oxygen layers. From the bonding geometry of the hydrogen bonds, it can be qualitatively concluded, that the oxygen-oxygen interactions induced by the hydrogen bonds fit easily into the higher pseudo symmetry of the AlO3 arrangement. (orig.)