Portal de Periódicos da CAPES

Crystal structure and lattice distortion of γ-NbN x and δ-NbN x

1980; IOP Publishing; Volume: 13; Issue: 32 Linguagem: Inglês

10.1088/0022-3719/13/32/008

1747-3802

G. Heger, O. Baumgartner,

Intermetallics and Advanced Alloy Properties

By means of neutron diffraction on single crystals the gamma and delta modification of NbNx is studied using samples with approximately the same x=N/Nb approximately=0.85. For the ordered gamma -NbN0.85 it was possible to refine a tetragonal distorted sodium chloride structure model in spite of the occurrence of twinning. The individual mean square displacements of the N and Nb atoms are compared with those of the disordered cubic delta -NbN0.84 and the dynamical components from previous inelastic neutron scattering investigations. For the delta -NbN0.84 single crystal only a small static distortion of the Nb and N sublattices is found. For gamma -NbN0.85 large static contributions to the mean square displacements of the N atoms occur whereas the sublattice of the Nb atoms is nearly undistorted. The group theoretical relationship between the structures of the gamma and the delta phase of NbNx is discussed.