Search results
Results from the WOW.Com Content Network
The angles that Bragg's law predicts are still approximately right, but in general there is a lattice of spots which are close to projections of the reciprocal lattice that is at right angles to the direction of the electron beam. (In contrast, Bragg's law predicts that only one or perhaps two would be present, not simultaneously tens to hundreds.)
Laue equations. In crystallography and solid state physics, the Laue equations relate incoming waves to outgoing waves in the process of elastic scattering, where the photon energy or light temporal frequency does not change upon scattering by a crystal lattice. They are named after physicist Max von Laue (1879–1960).
The reciprocal lattice is a term associated with solids with translational symmetry, and plays a major role in many areas such as X-ray and electron diffraction as well as the energies of electrons in a solid. It emerges from the Fourier transform of the lattice associated with the arrangement of the atoms. The direct lattice or real lattice is ...
Powder diffraction. Electron powder pattern (red) of an Al film with an fcc spiral overlay (green) and a line of intersections (blue) that determines lattice parameter. [1] X-ray powder diffraction of Y 2 Cu 2 O 5 and Rietveld refinement with two phases, showing 1% of yttrium oxide impurity (red tickers). Powder diffraction is a scientific ...
The reciprocal lattice is easily constructed in one dimension: for particles on a line with a period , the reciprocal lattice is an infinite array of points with spacing /. In two dimensions, there are only five Bravais lattices. The corresponding reciprocal lattices have the same symmetry as the direct lattice.
Bragg plane. In physics, a Bragg plane is a plane in reciprocal space which bisects a reciprocal lattice vector, , at right angles. [1] The Bragg plane is defined as part of the Von Laue condition for diffraction peaks in x-ray diffraction crystallography. Considering the adjacent diagram, the arriving x-ray plane wave is defined by:
Ewald's sphere. The Ewald sphere is a geometric construction used in electron, neutron, and x-ray diffraction which shows the relationship between: the wavevector of the incident and diffracted beams, the diffraction angle for a given reflection, the reciprocal lattice of the crystal. It was conceived by Paul Peter Ewald, a German physicist and ...
The size of the Ewald's sphere and hence the number of diffraction spots on the screen is controlled by the incident electron energy. From the knowledge of the reciprocal lattice models for the real space lattice can be constructed and the surface can be characterized at least qualitatively in terms of the surface periodicity and the point group.