An Electron Diffraction and Crystal Chemical Investigation of Oxygen/Fluorine Ordering in Niobium Oxyfluoride, NbO2F

Electron diffraction evidence for continuously variable, composition-dependent O/F ordering in the ReO3 type, NbV1−xNbIVxO2−xF1+x, 0⩽x⩽0.48, solid solution

“…A good example of this was found in a recent electron diffraction investigation [5][6][7] of Nb V O 2 F, of ReO 3 average structure type (see Fig. 1).…”

“…An additional complicating factor is that true, long range O/F ordering may not be required to satisfy local bond valence sum requirements, i.e. O/F ordering may not be complete in a full three-dimensional sense [3][4][5]. In this case, the diffraction evidence for local O/F ordering is not to be found in the average structure Bragg reflections, but rather takes the form of a highly structured diffuse intensity distribution.…”

“…Given the earlier electron diffraction results for the NbO 2 F end member [5], electron diffraction has again been used to look for diffraction evidence of O 2À /F À ordering within the ReO 3 type average structures of compounds within the Nb V 1Àx Nb IV x O 2Àx F 1+x solid solution field. Careful tilting experiments show that the reciprocal lattices at all compositions are again characterized by sheets of diffuse intensity, perpendicular to each of the three /001S directions, at the G7/hkqS Ã regions of reciprocal space.…”

“…1). This study [5] revealed the presence of characteristic planes of diffuse intensity running through the G7/hk1/3S Ã regions of reciprocal space (i.e. perpendicular to each of the major crystal directions a, b and c).…”

A low-temperature electron diffraction study of structural disorder and its relationship to the Kondo effect in ThAsSe

“…[22]) of the intensity distribution associated with both the diffuse 'lines' as well as the 'satellite reflections', e.g., the G7B0:14/1 % 10S Ã 7e/110S Ã diffuse 'lines' are most intense when looking out along the /1 % 10S Ã direction of reciprocal space and weakest along the orthogonal /110S Ã direction (particularly towards the edge of Fig. 2a) whilst the G7B0:28/100S Ã satellite reflections are most intense for G running along /010S Ã and have zero intensity for G running along /100S Ã is also apparent.…”