X-ray crystallography, << krihs tuh LAHG ruh fee, >> is a method for determining the three-dimensional arrangement of atoms in matter. The term X-ray crystallography refers to studies of substances, especially solids, in crystal form. However, the basic method used in X-ray crystallography can be applied to a broad range of materials that are not in crystal form.
In X-ray crystallography, a sample is exposed to a narrow monochromatic (single wavelength) X-ray beam. The X rays interact with the atoms in the sample and are diffracted (bent), much as sunlight is diffracted by a glass prism (see Diffraction ). The diffracted X rays produce a pattern of light and dark areas, commonly called the X-ray diffraction pattern. These light and dark areas are the result of constructive and destructive interference, the effect that occurs when two waves come together, on the diffracted X-ray beam (see Interference ). By studying the pattern, scientists can determine the three-dimensional arrangement of atoms in the sample, also called the molecular structure.
X-ray crystallography plays a vital role in such fields as chemistry, materials science, mineralogy, molecular biology, pharmacology, and polymer science. It can provide the accurate knowledge of molecular structures needed for the design of new drugs. X-ray crystallography can also be helpful in designing new materials, predicting the properties of new materials, and understanding how materials function.
