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Ian McDonald 1938-2020

Ian McDonald passed away peacefully in his Suffolk home on July 19th 2020. Although proud of his Scottish heritage, Ian was born in Southampton on April 16th 1938, after his parents moved south to England. His father died shortly after his birth. Ian attended Prior Park Public School in Bath. Later he earned a Physics Degree at the University of Hull; thereafter he engaged in experimental work towards a PhD at the University of Bangor in Wales, but eventually switched to theoretical research on nuclear magnetic resonance at the University of Nottingham. He then moved to Royal Holloway College near London as a postdoctoral research associate with Konrad Singer, after which he accepted a faculty position at Trinity College Dublin.

In 1967 Ian returned to Konrad Singer's group at Royal Holloway College (RHC). Together they pioneered Statistical Mechanics simulations in the UK. Specifically, they produced an early paper on histogram re-weighting (see: "Calculation of Thermodynamic Properties of Liquid Argon from Lennard-Jones Parameters by a Monte Carlo Method", Discussions of the Faraday Society 43, 40-49 (1967)). In a historic 1969 paper Ian was the first to introduce constant pressure Monte Carlo simulations (NPT Ensemble), which he extended in 1972 to mixtures. The same year Konrad and Ian organized a successful simulation workshop at RHC, attended, among others, by Loup Verlet, Daan Frenkel and Jean-Pierre Hansen. Another important work from that period, was produced by Ian, Konrad, and Evelyne Gosling. They pioneered non-equilibrium molecular dynamics (MD) at the same time as Bill Hoover in the USA (see: Molecular Physics 26, 1475, (1973)).

In 1973-74, Ian spent a year in Paris, where he worked in close contact with members of the Verlet group and researchers at CECAM in Orsay. This led to the start of strong interactions with life-long friends and collaborators, including Giovanni Ciccotti, Jean-Pierre Hansen, Gianni Jacucci and Mike Klein. In 1973, Ian was invited by Academic Press to write a book on the liquid state. He convinced Jean-Pierre Hansen to be co-author of the book, which was completed in 18 months and published in 1976. This first highly successful edition was followed by three thoroughly up-dated editions in 1990, 2006 and 2013.

In 1977 Josette Dupuy (ILL Grenoble) and AJ Dianoux organized the NATO Advanced Study Institute on Microscopic Structure and Dynamics of Liquids in Aleria (Corsica). This was one of the first Summer Schools devoted to liquids, and was attended by many distinguished colleagues, including Pierre-Gilles de Gennes, who gave the concluding address. Ian gave the introductory series of lectures on MD, which were highly appreciated. In 1978 Ian joined forces with Giovanni Ciccotti and Gianni Jacucci to introduce the concept of "Thought Experiments" by MD. This paper is considered a classic in the field.

In 1979 Ian was called to Cambridge, where he was appointed Teaching Fellow at Trinity College and Lecturer in Physical Chemistry at the Department of Chemistry. On moving to Cambridge, Ian engaged in fruitful collaborations with Ruth Lynden-Bell and other members of the thriving Department, including Stephen Elliott, while maintaining close links with colleagues from outside Cambridge, including Mauro Ferrario, Daan Frenkel, Jean-Pierre Hansen, Mike Klein, Paul Madden, Jean-Paul Ryckaert, Ilja Siepmann and their collaborators.

Over the years, Ian's interests broadened to ever more complex molecular, ionic and metallic states of matter, as well as to dense plasmas. In 1987, he joined forces with Giovanni Ciccotti and Daan Frenkel to publish "Simulations of Liquids and Solids", a collection of 49 key papers, from Metropolis et al. (1953) to Car and Parrinello (1985), accompanied by enlightening comments.

Ian did not shy away from administrative duties. From 1979 to 1985, and again from 1992 to 1994, Ian was the Editor of Molecular Physics. In his rigorous and demanding style, Ian did not hesitate to suggest improvements of presentation and language to authors of manuscripts, after they had been already accepted by referees. Ian demanded clarity and rigour of scientific presentations, and many of his collaborators owe him a large debt of gratitude for honing their scientific writing ability. Importantly, from 1994 to 2002, Ian served as Admissions Tutor at Trinity College Cambridge, a crucial and time-consuming job.

After his move to Cambridge, Ian acquired a small house in Huntingfield, a village near Halesworth in East Suffolk, close to the North Sea. This home he shared with his life partner Susan O'Gorman, his muse on all things mathematical. Later, Ian and Susan moved to “The Wicket”, their splendid 16th century cottage near Fressingfield in Suffolk. Working during weekdays in different places, Ian in Cambridge and Susan in Ipswich, they spent their weekends together in this idyllic cottage. They were warm and gracious hosts when Ian, quite often, invited a scientific visitor to join them and spend a relaxing period in the Suffolk countryside.

In December 2013, Ian and Susan attended a three-day meeting in Rome on the occasion of Giovanni Ciccotti's 70th birthday. After the meeting they stayed on to visit Rome. On Piazza Navona, Ian suffered a severe heart attack and was transferred urgently to the Royal Papworth Hospital near Cambridge, where he underwent massive heart surgery. It took him months to recover, but eventually he pulled through and resumed almost normal life. Sadly, Susan passed away on May 14th 2019, after a long fight with cancer. This was a terrible blow to Ian, from which he never recovered despite much attention from family, friends and colleagues.

Ian was a very private, self-effacing person. He supervised a small number of PhD students, including Ali Alavi and Ilja Siepmann. Notably, Ian did much of the computer programming for his research. Above all, he was a very rigorous scientist, and a loyal friend to many. Ian was very fond of nature and gardening, as was evident from the meticulous care he devoted to his gardens. Our community will sorely miss him. He was buried at the Church of St. Peter and St. Paul, in Fressingfield, Suffolk on August 10th 2020.

J.P. Hansen, M. Klein, D. Frenkel, P. Madden, J.P. Ryckaert, G. Ciccotti, M. Ferrario, A. Alavi, R. Lynden-Bell, M. Sprik

Acknowledgements: we are grateful to John Roberts, Malcolm and Diana Annis, and George Jackson for providing us with pertinent information.