Crystallography - feature Crystallography - feature STRUCTURAL BIOLOGY, GEOLOGY, ENGINEERING, CHEMISTRY, PHYSICS. BRAGG’S LAW. SPECTROMETERS. DIFFRACTOMETERS. PIONEERING WORK DONE AT LEEDS A CENTURY AGO STILL FEEDS INTO MUCH OF MODERN SCIENCE. THIS IS HOW IT STARTED The birth of X-ray crystallography For their achievements, William at Leeds in 1912-1913 through the and Lawrence Bragg were awarded work of Sir William Henry Bragg the 1915 Nobel Prize in Physics. In and his son Sir W. Lawrence Bragg 2013, the Braggs’ work was named was one of the culminating episodes the third most important British in arguably the most extraordinary innovation of the 20th century in an three decades in the physical sciences. online vote of 80,000 people. Between 1890 and the end of Yet research on crystallography the First World War, X-rays and had not even begun when the Braggs radioactivity were discovered, the arrived in England from Australia theories of relativity and quantum six years before the Nobel award. mechanics developed, and the Such immediate recognition is rare constitution of atoms first explained. for Nobel Prizes, and it testifies both During this period Marconi to the importance of their work and developed radio telecommunication, the clarity with which they explained the Wright brothers made their first and demonstrated its potential in flights and Max Planck proposed many areas of science. quantum theory. These were, in Cumbrian-born William came other words, the formative decades to Leeds from the University of of the modern age. Adelaide, Australia, where he had It is not often appreciated established a solid international how important to that incipient reputation for his work on modernity the Braggs’ work was. radioactivity and the nature of the William and Lawrence paved the new invisible ‘emanations’ from way to countless scientific and matter: X-rays, gamma rays and technological breakthroughs by alpha particles. As Professor of revealing the arrangement of atoms Physics and Mathematics, William in crystals. Although it had been long had found in Adelaide a meagre suggested that crystals were made laboratory, so he set about making up of a regular pattern of atoms and his own equipment by apprenticing molecules, there was previously no himself to a local instrument maker. way of knowing precisely how these When Leeds needed a new were arranged. Cavendish Professor of Physics in X-ray crystallography is the 1907, the English chemist Frederick chemist’s most reliable tool Soddy recommended William to the for deducing the shapes and University, saying that, when he had arrangements of molecules. It tells visited Adelaide, “I was much struck us about the nature of terrestrial with the spirit he has created around and extra-terrestrial minerals. him.” William was offered and Through an understanding of crystal accepted the post. THE BIRTH OF Sir William Henry Bragg structures, it became possible to In January 1909 William and explains the theory of develop new and better materials. his family – wife Gwendoline, sons reflecting light by prisms When applied to the molecules of Lawrence and Robert and daughter BY PHILIP BALL to school children at life, it ushered in the age of molecular Gwendy – boarded the coal-fired a 1931 lecture at the biology and genetics – most famously Watarah for the journey to England, Royal Institution. as the technique that revealed the arriving in Plymouth in March. Photo © Hutton-Deutsch structure of DNA to James Watson They rented a house in fashionable CRYSTALLOGRAPHY Collection/CORBIS and Francis Crick in 1953. Headingley as well as a weekend 6 — spring / summer 2013 spring / summer 2013 — 7 Crystallography - feature Crystallography - feature AFTER ONLY SIX YEARS THE BRAGGS WERE AWARDED A NOBEL PRIZE FOR THEIR WORK. NOT EVERYONE RECOGNISED THE IMPORTANCE OF BRAGG EXPLAINED THE IDEA OF THEIR WORK HOWEVER. “I WAS SO SHEETS OR PLANES OF ATOMS WITH A PLAQUE OUTSIDE THE PARKINSON EXCITED THAT I HAD TO TELL MY BRAGG X-RAY SPECTROMETER REFERENCE TO THE ROWS OF VINES BUILDING COMMEMORATES THE WORK AUNT ABOUT IT, WITH INDIFFERENT ENGLAND, 1910-1926 IN A VINEYWARD OF THE BRAGGS AT LEEDS SUCCESS,” WROTE LAWRENCE father was supreme at handling X-ray align and you can see them stretching gathering of Europe’s top physical A LEEDS GRADUATE: tubes and ionization chambers. You away in parallel formation. scientists – was a particularly must find it hard to realize these days On this basis, Lawrence worked prestigious platform, and at the FROM LEEDS TO MARS what brutes X-ray tubes then were.” out how the reflection angles of the 1913 meeting on “The Structure At Leeds, William had rather better spots depend on the distances between of Matter” William discussed his Would the Braggs ever have looked technical support than Lawrence did sheets and the wavelength of the work with Albert Einstein and Marie up at Mars and imagined that, one in Cambridge, which still pursued X-rays. He expressed this in a formula Curie, along with several scientists, day, an X-ray spectrometer would PHOTO: a “sealing wax and string” approach now known as ‘Bragg’s law,’ which such as Leon Brillouin and Frederick W. LAWRENCE BRAGG, be there, gathering data on the to experimentation. William, in first appeared in a paper presented to Lindemann, who went on to make WHO WORKED WITH planet’s surface? Although only the contrast, enjoyed the services of the Cambridge Philosophical Society important contributions to the HIS FATHER AT LEEDS size of a tin can, the Alpha Particle WHILST A STUDENT AT an excellent workshop led by head in November 1912 and was reported understanding of diffraction and CAMBRIDGE X-ray Spectrometer (APXS), mechanic C H Jenkinson. in Nature in December. Here he also crystal structure. developed by the Canadian Space It was Jenkinson who built, from showed that, by assuming a particular Late in 1914, William wrote CREDIT: Agency (CSA), MDA robotics and SCIENCE & SOCIETY William’s design, a revolutionary kind of arrangement of atoms in a long letter to the Leeds Vice- PICTURE LIBRARY Professor Ralf Gellert’s science instrument that could be used crystals of zinc sulphide, he could Chancellor Michael Sadler, pointing team at University of Guelph, both to measure X-ray wave account perfectly for the X-ray pattern. out the University’s pre-eminence Canada, is sending an enormous lengths (the technique of X-ray The Braggs’ crucial realisation was in X-ray diffraction. “The practical amount of data about the geology spectrometry) and to measure that, if the X-ray diffraction pattern applications are likely to be of no of Mars back to Earth. Attached reflections from crystal plains could be accurately predicted from a less importance than the theoretical,” by an arm to NASA’s Curiosity (X-ray diffraction). The instrument, crystal structure, then one could also he wrote. Although his request rover, the instrument determines used both as a spectrometer and a work backwards, deducing from the for funds was supported, Leeds the chemical composition of the diffractometer, partly superseded experimentally measured pattern, the couldn’t match the offer in early rocks and soil in the red planet’s Laue’s photographic technique in structure of the crystal itself. 1915 of a professorship from wealthy Gale Crater. that it enabled precise measurements Of all the crystals whose structures University College London (UCL). CSA’s mission scientist for of the angles and intensities of the were worked out principally during William at first refused the offer, but Curiosity is a physicist who diffracted beams. 1913 (sodium chloride, potassium by the time he accepted their second studied at Leeds. Vicky Hipkin Adhering to William’s ‘corpuscular’ chloride, calcium fluoride, zinc offer he had decided he needed to (PhD Atmospheric Physics 2000), view of X-rays, the Braggs at first sulphide and diamond) it was the be in London at the centre of the Senior Program Scientist, Planetary sought to interpret Laue’s bright structure of iron sulphide which gave war effort. Exploration, says “Curiosity’s X-ray spots on the basis that X-ray Lawrence “the greatest thrill,” as he William’s departure was not APXS is amazingly sensitive given AT THE 1913 MEETING ‘particles’ were being channelled recorded long afterwards. This was the necessarily the tragedy for Leeds ON “THE STRUCTURE its small size. William Henry along ‘avenues’ between rows of first structure in which the positions of that it might have seemed at the OF MATTER” WILLIAM Bragg’s spectrometer at Leeds has atoms, an idea they described in a the (sulphur) atoms were determined time. The Braggs’ seminal work BRAGG DISCUSSED been miniaturised using modern HIS WORK WITH paper published in October 1912 in from the intensity (brightness) of the here inevitably left a legacy. In 1929 ALBERT EINSTEIN AND technologies – the silicon drift the journal Nature. reflections. Lawrence recalled that “I William’s student William Astbury, MARIE CURIE detector and sensitive electronic cottage near Bolton Abbey 20 miles Given this interest, the Braggs, But later that month, shortly worked it out in the drawing room of who worked with him at UCL circuitry for pulse detection. north of the city. Lawrence enrolled, father and son, were fascinated by PHOTO: after his return to Cambridge for our house in Leeds and was so excited and later at the Royal Institution APXS data are very important as his father had 28 years earlier, at news of work in Munich by Max WILLIAM HENRY the Michaelmas term, Lawrence hit that I had to tell my aunt who was in London, came to Leeds as a to geochemists on the Curiosity BRAGG WITH HIS Trinity College, Cambridge. Laue, a student of Max Planck. Laue SPECTROMETER, on a novel explanation.