X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

, wide-angle X-ray scattering (WAXS) or wide-angle X-ray diffraction (WAXD) is the analysis of Bragg peaks scattered to wide angles, which (by

Bragg's law In physics and chemistry , Bragg's law, Wulff–Bragg's condition or Laue–Bragg interference, a special case of Laue diffraction, gives the angles for coherent scattering of waves from a crystal lattice. It encompasses the superposition of wave ...

) are caused by sub-nanometer-sized structures. It is an X-ray-diffraction method and commonly used to determine a range of information about crystalline materials. The term WAXS is commonly used in

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

sciences to differentiate it from SAXS but many scientists doing "WAXS" would describe the measurements as Bragg/X-ray/powder diffraction or

crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wor ...

. Wide-angle X-ray scattering is similar to

small-angle X-ray scattering Small-angle X-ray scattering (SAXS) is a small-angle scattering technique by which nanoscale density differences in a sample can be quantified. This means that it can determine nanoparticle size distributions, resolve the size and shape of (monodis ...

(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 Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, Transparency and translucen ...

samples. It can also be used to determine the chemical composition or phase composition of a film, the texture of a

film A film also called a movie, motion picture, moving picture, picture, photoplay or (slang) flick is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, feelings, beauty, or atmosphere ...

(preferred alignment of crystallites), the crystallite size and presence of film

stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...

. 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

X-ray scattering Diffraction {{spectroscopy-stub