Great Solid-State Physicists of the 20th Century, edited by Julio A. Gonzalo and Carmen Aragó López

The five great solid-state physicists selected for this book are William Henry Bragg and William Lawrence Bragg (WHB and WLB, father and son), Peter Debye, John Bardeen and Lev Landau. In this centenary year (2012) of X-ray diffraction, it is particularly appropriate to revisit the lives of these great twentieth-century Nobel Prize-winners, who contributed so much to the so-called ‘Century of Solid-State Physics’ – the determination of crystal structures; the birth of solid-state electronics; the drive for miniaturization in computers; ever better resolution in detectors for particle physics and cosmology; and new magnetic, piezoelectric and electro-optic materials for everyday use. The book has two or three chapters on each of these physicists; and concludes with a chapter on the relevance of materials science followed by a list of all Nobel Prize-winners in Physics together with biographical details of those connected with the solid state. Michael Glazer (Oxford) has here written a brief family history of the Braggs and a lucid account of the early days of X-ray diffraction. Roentgen’s momentous discovery of X-rays in 1895 sent scientists throughout the world experimenting with this mysterious invisible radiation (without any safety regulations!), but the discovery of X-ray diffraction was not to be made until many years later. There was controversy over whether X-rays consisted of particles or of waves. As is now well-known, in 1912, Max von Laue suggested to Walter Friedrich and Paul Knipping that they should try directing a beam of X-rays on to a crystal of copper sulphate. The resulting diffraction pattern showed that X-rays could indeed behave as waves, and that they had a wavelength comparable to the inter-planar spacing of atoms in the crystal. Von Laue however had thought that the X-rays taking part were all of a particular wavelength (five of them in fact); but WLB (later Sir Lawrence Bragg) was able to account for the positions of all the spots in Laue’s photographs by assuming that the X-rays were polychromatic and had interfered by reflexion from parallel planes of atoms. In 1913, WHB built the first ionization spectrometer to study X-ray diffraction using counter techniques – the forerunner of the diffractometer used by crystallographers to solve crystal structures throughout the world today. When the Great War erupted in 1914, WLB joined the British Army and designed sound-ranging equipment to locate enemy guns. During that year, von Laue was awarded the Nobel Prize for Physics; and in the following year, while at the war front at Ypres, WLB learnt that he and his father had been awarded the next prize! WLB was only 25 – still the youngest ever Nobel Prize-winner by several years. WHB and WLB solved the structures of many simple crystals, such as the alkali halides, but their results were not always readily accepted by some chemists, who years later still clung to the idea of assemblies of well-defined individual molecules. Father and son decided to divide crystallography between them: WHB taking organic crystals while WLB would continue with inorganic ones. They both encouraged women to take up scientific careers and this

Field of study: Materials science