Interstitial Point Defects (D,N,O) in Transition Metals
Diffuse neutron or X-ray scattering close to the Bragg peaks (Huang scattering) and far away from Bragg peaks (Zwlschenreflex-scatterlng) supplies detailed information on point defects and small agglomerates in crystals . The defect structure, i.e. the lattice location, the displacements of the near neighbours and the strength and symmetry of the long ranged displacement field can be determined. In order to demonstrate the power of this technique, we report on recent experimental results. Interstlllally dissolved N and O in Nb are located on octahedral sites and create rather large displacements in their vicinity. Their long ranged displacement field shows the symmetry of the defect site. The light Interstltlals H and D in Nb are located on tetrahedral sites and their long ranged displacement field shows the symmetry of the host lattice. A rather complicated defect model is necessary in order to explain the local defect structure.
KeywordsMobile State Octahedral Site Lattice Distortion Bragg Peak Tetrahedral Site
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