X-ray crystallography

X-ray crystallography is a technique used for determining the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder and various other information.

History

X-ray crystallography was first used by William Lawrence Bragg and his father, William Henry Bragg, in 1912, following the discovery of X-ray diffraction by Max von Laue in 1912. The Braggs were awarded the Nobel Prize in Physics in 1915 for their work in this field.

Principles

The basic principle behind X-ray crystallography is Bragg's law, which states that the angles at which a crystal will diffract X-rays are directly related to the size and shape of the unit cell of the crystal. This law is used to determine the distances between planes of atoms within the crystal, which in turn provides information about the crystal's structure.

Applications

X-ray crystallography has been used in a wide range of fields, including chemistry, physics, materials science, geology, and biology. It has been instrumental in the development of many drugs, as it allows scientists to determine the structure of complex molecules such as proteins and DNA.

See also

• Crystallography
• X-ray diffraction
• Bragg's law
• Crystal structure
• Protein crystallography

X-ray crystallography

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  Interferenz-Erscheinungen bei Röntgenstrahlen Tafel II Fig. 5
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