Jim came to Brown University as a full Professor in 1989 from Los Alamos National Laboratory and was named the Jesse H and Louisa D Sharpe Metcalf Professor of Chemistry from 1995 until his retirement in 2014. He obtained his Ph.D. degree from Harvard in 1971 and was a faculty member at the Univ. of Illinois and at SUNY Stony Brook and a staff scientist at Los Alamos National Lab before coming to Brown.
Jim was one of the world's premier experts on using computer simulation techniques to model the motions of atoms and molecules. He made seminal contributions to the study of molecular motion on metal surfaces and to the atomic clusters, but it was his creative insights into how to exploit ideas from probability and statistics to drive simulation methods that made him such a widely respected figure in the theoretical chemistry community.
His development of what he called, in his characteristically irreverent way, "randomly exact" methods, for looking at quantum mechanical problems aided numerous researchers in the chemical physics field. He also made countless and varied contributions to the long-standing problem of modeling infrequent events. In particular, his early insights into what later came to be called "replica exchange techniques," but which he (in typical fashion) preferred to call "j-walking" methods set the stage for much of modern bimolecular simulation.
With the aid of numerous students and colleagues, including his long-time collaborator David Freeman at the University of Rhode Island, and Paul Dupuis at Brown University, he made an indelible mark on all of us who (in one of his favorite quotes) like use to computers to gain "insights, not numbers."
Jim is survived by his wife Margaret, DEEPS and Chemistry, Scientific Computing Coordinator (emeritus), a son John and his family.