Editing Wide-angle X-ray scattering

{{Short description|Technique in X-ray crystallography}}
{{Refimprove|date=December 2011}}
In [[X-ray crystallography]], '''wide-angle X-ray scattering''' ('''WAXS''') or '''wide-angle X-ray diffraction''' ('''WAXD''') is the analysis of [[Bragg peak]]s scattered to wide angles, which (by [[Bragg's law]]) are caused by sub-nanometer-sized structures.<ref>{{cite journal | last=Podorov | first=S. G. | last2=Faleev | first2=N. N. | last3=Pavlov | first3=K. M. | last4=Paganin | first4=D. M. | last5=Stepanov | first5=S. A. | last6=Förster | first6=E. | title=A new approach to wide-angle dynamical X-ray diffraction by deformed crystals | journal=Journal of Applied Crystallography | publisher=International Union of Crystallography (IUCr) | volume=39 | issue=5 | date=2006-09-12 | issn=0021-8898 | doi=10.1107/s0021889806025696 | pages=652–655}}</ref> It is an [[X-ray diffraction|X-ray-diffraction]]<ref>"WIDE-ANGLE X-RAY DIFFRACTION THEORY VERSUS CLASSICAL DYNAMICAL THEORY" by S.G. Podorov, A. Nazarkin, Recent Res. Devel. Optics, 7 (2009) {{ISBN|978-81-308-0370-8}}</ref> method and commonly used to determine a range of information about crystalline materials. The term WAXS is commonly used in [[polymer]] sciences to differentiate it from SAXS but many scientists doing "WAXS" would describe the measurements as Bragg/X-ray/powder diffraction or [[crystallography]]. 

Wide-angle X-ray scattering is similar to [[small-angle X-ray scattering]] (SAXS) but the increasing angle between the sample and detector is probing smaller length scales. This requires samples to be more ordered/crystalline for information to be extracted. In a dedicated SAXS instrument the distance from sample to the detector is longer to increase angular resolution. Most diffractometers can be used to perform both WAXS and limited SAXS in a single run (small- and wide-angle scattering, SWAXS) by adding a beamstop/knife edge. 

==Applications==
The WAXS technique is used to determine the degree of [[crystallinity]] of [[polymer]] samples.<ref>{{Cite journal|last=Murthy|first=N. S.|last2=Minor|first2=H.|date=1990-06-01|title=General procedure for evaluating amorphous scattering and crystallinity from X-ray diffraction scans of semicrystalline polymers|journal=Polymer|volume=31|issue=6|pages=996–1002|doi=10.1016/0032-3861(90)90243-R|issn=0032-3861}}</ref> It can also be used to determine the chemical composition or phase composition of a film, the texture of a [[Thin film|film]] (preferred alignment of crystallites), the crystallite size and presence of film [[Stress (mechanics)|stress]]. As with other diffraction methods, the sample is scanned in a wide-angle X-ray [[goniometer]], and the scattering intensity is plotted as a function of the 2θ angle. 

X-ray diffraction is a non destructive method of characterization of solid materials. When X-rays are directed at solids they scatter in predictable patterns based on the internal structure of the solid. A crystalline solid consists of regularly spaced atoms (electrons) that can be described by imaginary planes. The distance between these planes is called the d-spacing. 

The intensity of the d-space pattern is directly proportional to the number of electrons (atoms) in the imaginary planes. Every crystalline solid has a unique pattern of d-spacings (known as the powder pattern), which is a fingerprint for that solid. Solids with the same chemical composition but different phases can be identified by their pattern of d-spacings.

==References==
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{{X-ray science}}
[[Category:X-ray scattering]]
[[Category:Diffraction]]


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