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The Ewald sphere is a geometric construct used in X-ray crystallography which neatly demonstrates the relationship between:
Additional recommended knowledge
It was conceived by Paul Peter Ewald, a German physicist and crystallographer.
Ewald's sphere can be used to find the maximum resolution available for a given x-ray wavelength and the unit cell dimensions. It is often simplified to the two-dimensional "Ewald's circle" model or may be referred to as the Ewald sphere.
A crystal can be described as a lattice of points of equal symmetry. The requirement for constructive interference in a diffraction experiment means that in momentum or reciprocal space the values of momentum transfer where constructive interference occurs also form a lattice (the reciprocal lattice). For example, the reciprocal lattice of a simple cubic real-space lattice is also a simple cubic structure. The aim of the Ewald sphere is to determine which lattice planes (represented by the grid points on the reciprocal lattice) will result in a diffracted signal for a given wavelength, λ, of incident radiation.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ewald's_sphere". A list of authors is available in Wikipedia.|