One hundred years of diffuse x-ray scattering

It is not generally appreciated that X-ray diffuse scattering has been known for almost as long as the Bragg scattering that is used in crystal structure determination. While we are celebrating the centenary of the birth of crystallography, marked by the first diffraction of X-rays by a crystal (Laue) and the formulation of Bragg's Law that laid the foundation for crystal structure determination, it is salutary to remember that diffuse scattering was observed in the very earliest experiments. Within a few years, in a paper on mixed crystals, Laue showed that occupational disorder produces a continuous background scattering between the Bragg peaks - the so-called Laue monotonic scattering. In this brief review, we trace the development of diffuse scattering methods over the course of a century.