A tribute to Alan Soper – foreword by the editors

This special issue of Molecular Physics is a collection of papers to mark the retirement and honour the remarkable scientific contributions of Dr. Alan Kenneth Soper FRS. Over an active research career spanning more than four decades, Alan has developed state-of-the-art neutron-scattering instrumentation, experimental and analytical techniques, and computational methods that collectively have transformed our understanding of the atomic and molecular structure of liquids and other structurally disordered systems. The summary leading to his election as Fellow of the Royal Society in 2014 says it all: Alan Soper is distinguished as the world-leading experimentalist on the structure of water and aqueous solutions, and an internationally outstanding expert on the structure of liquids in general. Besides making major and seminal contributions to the study of water and other aqueous systems, including complex systems of high chemical and biological importance, he has been influential in studies of many other liquids and glasses, and has developed novel diffraction instruments and techniques that have revolutionised the field. He has also pioneered the wider use of computer simulation as a tool for building three-dimensional models of the disordered states of matter based on measured data [1].

Born in 1951 in Romford, Essex, Alan went on to study physics at the University of Leicester in the UK. On completing his BSc in 1973, he chose to stay in Leicester to undertake a PhD under the supervision of Prof. John Enderby, using neutrons to investigate the structure of aqueous solutions. On completing his PhD in 1977, Alan then moved to the University of Guelph in Ontario, Canada, to continue developing his skills in neutron scattering and undertake a postdoctoral fellowship with Prof. Peter Egelstaff. From Guelph, over the period 1979–1982, Alan was referred to the Los Alamos National Laboratory in the USA to build a General Purpose Diffractometer at the laboratory’s fledging pulsed neutron source. After Los Alamos, Alan moved back to Guelph to spend four years as an assistant professor, before choosing to return to the UK in 1986 to take up a post as a staff scientist at the newly constructed ISIS Pulsed Neutron Source of the Rutherford Appleton Laboratory. Since then, he spent the next thirty-plus years of his career at this facility in Oxfordshire, leading the development of world-leading neutron-scattering instrumentation – first the SANDALS diffractometer, followed by GEM and NIMROD. In parallel, Alan also developed new techniques to facilitate the application of hydrogen–deuterium isotopic-substitution methods to bring to an entirely new level the insights that neutrons could provide into the properties of molecular liquids and liquid mixtures. Additionally, he invented new computational methods for ultimately transforming neutron-scattering data into three-dimensional atomistic models of liquids and amorphous materials, most notably the now widely used technique of Empirical Potential Structure Refinement. Over the years, all of these seminal contributions have enabled ISIS to grow and support a large and thriving scientific community, whose interests range across a vast cross-section of scientific disciplines – from pure physics, chemistry and biology, to more applied subjects such as materials science, environmental science or chemical engineering. To date, Alan has authored over 300 research publications that have attracted over 18000 citations, and these figures continue to be on the rise!

As guest editors, we feel privileged to have been able to put together this special issue over the past year. We would also like to thank the many colleagues and friends who have contributed to this venture, those who have assisted us as referees and advisors, as well as the staff of Molecular Physics for their diligence and support along the way. We join them all in wishing Alan a long and happy retirement, as well as many more opportunities for him to continue informing and educating us with his keen scientific insight.

Thank you Alan, the floor is now yours [2]!