IN THE 1950s and 1960s the physicist William Cochran did pioneering work on many of the problems that underpinned Nobel prizes won by others, including the structure of DNA.
He also worked on so-called 'direct methods'; for determining the arrangement of atoms in crystal structures and on the interpretation of the way atoms vibrate in solids. He was responsible for advances in the theoretical understanding of the way crystalline solids transform from one structure to another at structural phase transitions.
Bill Cochran was born in 1922 and educated at Boroughmuir High School in Edinburgh before going to Edinburgh University to read physics. After graduating in 1943 he decided that his postgraduate studies would be best pursued in the chemistry department. There he worked with Arnold Beevers on the crystal structures of organic compounds, as well as fulfilling his wartime obligations as an air-raid warden. He left Edinburgh in 1948 to go to Cambridge, where he held a succession of posts until 1964.
During this period he did much of the research work for which he is now known. His skills in determining the complex crystal structures of organic molecules led Francis Crick to seek his help in understanding the diffraction patterns of DNA, and his elegant explanation of the scattering from a helix was a crucial step in enabling Crick and Watson to determine the structure of DNA.
Around the same time, he made a breakthrough in showing how to ex-ploit the systematic relationships between the intensitiesone of the very first truly precise measurements of electron density in a crystal, and wrote, with Henry Lipson, The Determination of Crystal Structures, the definitive text for a generation of crystallographers.
His research took a very different turn in 1958-59, when he spent a sabbatical year with Bert Brockhouse at the laboratories of Atomic Energy of Canada Ltd. Brockhouse, who subsequently won a Nobel Prize, had just made his novel triple-axis spectrometer, which was used to study the crystal dynamics of solids. This was done using slow neutron scattering, from which Brockhouse obtained his first data, using a crystal of sodium iodide. Analysis then revealed that the old model of the crystal dynamics was inadequate. So Cochran developed a more correct model, in which the outer shell of the electrons became displaced from the nucleus and the core electrons. This attracted wide attention, especially when applied to other alkali halides and to semiconductors.
Further developments led to a new understanding of ferroelectricity in a crystal — a property now of high interest in a wide range of device applications. This understanding was later generalised by Cochran and extended into other fields of physics and chemistry.
In 1964 Cochran was appointed Professor of Physics at Edinburgh University, and established a new research group in condensed matter physics. Forty years on, his successes continue to bear fruit and Edinburgh retains a reputation as a leader in this field. Cochran helped to create the modern department of physics, and became head of it in 1975. In the decade up to his retirement he played an increasing role in the university’s administration, becoming vice-principal from 1984 to 1987.
Cochran was a Fellow of the Royal Societies of London and Edinburgh, and a fellow and then honorary Fellow of Trinity Hall, Cambridge. Among other honours, he was awarded the Guthrie Medal by the Institute of Physics, the Hughes Medal of the Royal Society and the Potts Medal of the Franklin Institute. A proud Scotsman, he took a keen interest in his family background, in Scots verse and in the country around his cottage near Callendar.
He is survived by his wife, whom he married in 1953, and by their son and two daughters.
William Cochran, physicist, was born on July 30, 1922. He died on August 28, 2003, aged 81.