Difference between revisions of "Debye-Waller factor"
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== Restrictions == | == Restrictions == | ||
| − | Normally, the following restrictions apply to the anisotropic B-factor tensor | + | Normally, the following restrictions apply to the [http://en.wikipedia.org/wiki/Anisotropic anisotropic] B-factor tensor |
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== External links == | == External links == | ||
* [http://en.wikipedia.org/wiki/Debye-Waller_factor Wikipedia article on '''Debye-Waller factor'''] | * [http://en.wikipedia.org/wiki/Debye-Waller_factor Wikipedia article on '''Debye-Waller factor'''] | ||
| + | * [http://www.ocms.ox.ac.uk/mirrored/xplor/manual/htmlman/node296.html Overall B-Factor Refinement] | ||
[[Category:Crystallography]] | [[Category:Crystallography]] | ||
Revision as of 23:41, 27 September 2006
The Debye-Waller factor, also known as the B-factor or the temperature factor describes the decrease in scattering intensity (either from x-ray or neutron scattering) due to the thermal motion of the atoms, or due to crystal disorder. The thermal motion, or disorder, in some sense reduces the validity of the Laue diffraction condition which is based on fixed atoms.
I = I_0 * exp(-1/3 * |G|^2 * u^2)
I is the weakened intensity and I0 the source intensity. G is a reciprocal lattice vector and u the thermally enhanced oscillation amplitude of the atoms.
Higher orders of Bragg reflection are weakened more.
Restrictions
Normally, the following restrictions apply to the anisotropic B-factor tensor
| Triclinic | none |
| Monoclinic | B13 = B23 = 0 when β = α = 90° B12 = B23 = 0 when γ = α = 90° |
| Orthorhombic | B12 = B13 = B23 = 0 |
| Tetragonal | B11 = B22 and B12 = B13 = B23 = 0 |
| Rhombohedral | B11 = B22 = B33 and B12 = B13 = B23 |
| Hexagonal | B11 = B22 and B13 = B23 = 0 |
| Cubic | B11 = B22 = B33 and B12 = B13 = B23 = 0 |
