DEVELOPING AND DESIGNING NEW CHEMICALS AND MATERIALS - Chemistry: Notable Research and Discoveries - page 8

Certain mathematical techniques can determine molecular structure from
X-ray diffraction images, such as this X-ray diffraction image of a protein.
(Alfred Pasieka/Photo Researchers, Inc.)
The first step in many techniques that visualize a substance's struc-
ture is to make a crystal. A crystal is a solid substance in which the mol-
ecules are packed in repeating, geometric arrangements. Many, though
not all, substances will form crystals under certain conditions, and in
general the process does not alter the structure of the molecules be-
ing crystallized. When bombarded with X-rays, a crystal scatters the
radiation, but not in a random fashion. The direction and intensity of
the scattered X-rays depends on the geometry of the crystal, and X-ray
detectors record the resulting patterns. With a mathematical technique
developed by the German physicist Max von Laue (1879-1960) and the
British father and son team Sir William Henry Bragg (1862-1942) and
Sir William Lawrence Bragg (1890-1971) in the 1910s, researchers can