William and Lawrence Bragg and modern material science
Michael Glazer, Visiting Professor at the University of Warwick
The resulting structural arrangement, with alternating Na and Cl atoms, in all directions caused a degree of disbelief in the chemistry community who had expected that the Na and Cl atoms would form discrete molecular units. A. Smithells, Professor of Chemistry in Leeds, even begged Lawrence to “please make the chlorine atoms a little closer to the sodium!”
It took several years for Lawrence’s structure to be accepted by chemists. Another paper followed, this time by both William and Lawrence, on the structure of diamond. They both worked throughout 1913 and into 1914 making further developments in this new science. Then came the Great War.
Lawrence was sent to France, working in a unit developing sound-ranging techniques to locate the presence of enemy guns, a project which turned out to be most successful. In 1915, while still at the front, he received a telegram informing him that he and his father had been awarded the 1915 Nobel Prize in Physics. To this day, William and Lawrence are the only father and son team to receive the Nobel Prize and Lawrence remains the youngest Nobel winner ever.
After the war, William and Lawrence set up their own research groups. William went to University College London before moving on to the Royal Institution. Meanwhile, Lawrence took up a professorship in the Schuster Laboratory at the University of Manchester. In order to avoid researching the same topics at the same time, they agreed that William would concentrate mainly on crystals of organic molecules, while Lawrence would concentrate on metals and inorganic materials. During this period they made a number of contributions to the development of new techniques used to extract structural information from diffraction data. Around this time, diffraction by crystals of neutrons and electrons was also discovered (these discoveries were also honoured by Nobel prizes) and this extended the range of methods for studying crystal structures.
The Braggs were responsible for encouraging women into science. Both of them built up large research groups and both of them included a high proportion of female scientists in those groups, which was unusual for the time. Out of 18 of William’s students, 11 were women. Lawrence similarly included several female students in his research group when he became Professor of Physics at Manchester. One of William’s most successful female students was Kathleen Lonsdale (née Yardley) who worked out the crystal structure of hexamethyl benzene. This proved for the first time that the benzyl group, consisting of a ring of six carbon atoms, was flat rather than puckered. This time, chemists were happy. It had been predicted that this would be the case and, had it turned out otherwise, much of organic chemistry as it was at the time would have had to be rewritten. Lonsdale later became one of first women to be elected to a Fellowship of the Royal Society.
The lineage of scientists that stem from the Braggs is impressive. Another of William’s students was Desmond “Sage” Bernal and one of Bernal’s students was the crystallographer Dorothy Hodgkin (née Crowfoot), who later obtained the Nobel Prize for her work on penicillin and vitamin B12. Hodgkin’s work on the structure of potassium benzyl penicillin was an important step in the development of new penicillin-based antibiotics. Alongside Hodgkin, another female student of Bernal was Helen Megaw who worked on the structure of ice and on many important minerals such as feldspars and perovskites.
William died in 1942. By this time, Lawrence had been appointed Cavendish Professor at the Cavendish Laboratory in Cambridge. There he established the Crystallography Laboratory. Among the scientists attracted to the new lab was the Austrian exile, Max Perutz. Perutz worked closely with Lawrence to elucidate the complicated structure of the haemoglobin molecule; known for its ability to transport oxygen in the blood. Also in the laboratory, and working on the structure of myoglobin, was John Kendrew and this work finally enabled both structures to be found. Around this time, Francis Crick and James Watson had taken up the problem of the structure of DNA – also working in the Cavendish Laboratory. Crick and Watson, collaborating with Maurice Wilkins and Rosalind Franklin at King’s College London, eventually showed that Franklin’s X-ray photographs proved that DNA consisted of a double helix, and this finally showed the means by which reproduction occurred, leading to the modern science of genetics.
Kendrew and Perutz received the Nobel Prize in Chemistry in 1962 and, in the same year, Wilkins, Crick and Watson received the Nobel Prize in Physiology or Medicine; a unique occasion in which scientists from the same laboratory obtained two Nobel Prizes at the same time! It seems that Lawrence Bragg knew how to pick winners.
On his retirement in 1954, Lawrence became Director of the Royal Institution (Ri). He became famous for his lecturing skills in which he explained many complex areas of science using clever demonstrations constructed by his laboratory assistant Brian Coates. Lawrence instituted a series of lectures for schools: these were extremely popular and it is considered that some 20,000 school children per year (including myself) attended them while he was at the Ri. He retired in 1966.
The legacy created by the two Braggs is profound. First of all, had they not made their initial discoveries 100 years ago, the honour of founding X-ray crystallography might have occurred in Germany rather than in Britain. It would have delayed the realization that crystal structures could be determined by diffraction, and this would have affected the development of new materials: the electronics industry would have been affected since knowledge of semiconductor, metal and insulator structures is essential for the invention of all electronic devices. Again, structure determination of biologically based materials would have suffered and one wonders if the modern field of genetics, protein structures, antibiotics and other pharmaceutical development would have occurred. Modern material science has relied, almost in its entirety, on that early discovery by the Braggs.
Most crystallographers today, especially in the UK, can trace their ‘scientific family’ back to one of the Braggs. In my own case, my PhD supervisor was Dame Kathleen Lonsdale, a student of William Bragg (thus making William my ‘crystallographic grandfather’!). My own students can claim him as their crystallographic great-grandfather! Similarly, Professor Pamela Thomas, from the Department of Physics at Warwick, is also a crystallographic great-grandchild of William.
Professor Michael Glazer, Visiting Professor at the University of Warwick and Emeritus Professor of Physics at the University of Oxford. Mike’s research interests are in the relationship between crystal structure and physical properties; crystallographic instrumentation. His hobby is flying; he owns a 2005 Cirrus SR22, which he flies everywhere, especially to and from France.
Image: Braggs images c/o The Royal Institution of Great Britain.