William Wayne Wood, a leader in the development of the Monte Carlo (MC) method in statistical physics and in the modern theory of detonation, died of cancer on 12 July 2005 in Los Alamos, New Mexico. He was an untiring devotee of the maxim that “the language of physics is mathematics,” to the effect that virtually every problem to which he applied his hand was remarkably clarified. In addition to serving on advisory panels and as a group leader, he was the prime mover in the establishment of the postdoctoral program at Los Alamos National Laboratory.
Bill was born on 1 November 1924 in Terry, Montana, and, following the early death of his parents, was raised in a foster home on a Montana farm. His education at Montana State College, Bozeman, was interrupted by his service in the US Navy during World War II. He was a radar officer as part of the occupation of Japan and was released from active duty in May 1946.
Bill completed his studies at Montana State and graduated with a BS in chemistry with honors in June 1947. He matriculated to Caltech in September of that year, and earned his doctorate in chemistry and physics in June 1951 under the direction of John G. Kirkwood.
Joining the explosives division at Los Alamos in 1950, Bill turned his attention from his quantum chemical thesis to both classical statistical mechanics and the statistical analysis of experimental data. After getting his feet wet by analyzing the equation of state of hard spheres in the free-volume limit, he combined the two statistical disciplines when he undertook the extension of the MC method of the Los Alamos group (Nicholas Metropolis, Marshall and Arianna Rosenbluth, and Augusta and Edward Teller) to soft interaction potentials; in addition to reporting the first rigorous estimates (always with statistical uncertainties!) of the pressure and internal energy of a fluid modeled by the Lennard-Jones 6–12 potential, he laid the mathematical foundation of the MC method as a Markov process.
When in 1956 Bernie Alder at the Lawrence Radiation Laboratory (now the Lawrence Livermore National Laboratory) initiated molecular dynamics (MD) calculations of the equation of state of hard spheres and obtained results that appeared to disagree with the Los Alamos group’s results, Wood and Alder undertook a celebrated collaboration to reconcile those revolutionary techniques. Wood, using Monte Carlo, and Alder, using molecular dynamics, explored the equations of state of hard spheres and of disks, to ascertain their agreement and demonstrate the power of the methods, especially with regard to the existence of the fluid–solid phase transition.
In parallel with his statistical mechanical interests, and in collaboration first with Kirkwood and later with Zevi Salsburg, Bill addressed the problem of detonation structure. During World War II, Yakov Zeldovitch, John von Neumann, and Werner Doering (ZND) had independently proposed that a detonation consists of a shock wave followed by a zone of exothermic chemical reaction that ends in an equilibrium state moving at the local sound speed with respect to the shock, but the theory contained a fundamental ambiguity. The Wood– Salsburg reformulation integrated the concept of partial thermodynamic equilibrium and applied stability results from both thermodynamics and nonlinear differential equations to the reactive Euler equations to resolve the ambiguity. The framework so created formed the basis for later structural and hydrodynamic-stability studies.
Combining MC and MD techniques in collaboration with E. G. D. Cohen of Rockefeller University in the late 1960s, Bill undertook the study of nonequilibrium statistical mechanics with a calculation of self-diffusion for the Ehrenfest wind-tree model. When Alder reported MD results that suggested the slow decay of the velocity autocorrelation function for hard spheres and disks, Bill turned to the comparison of the numerical results to the kinetic theory and the mode-coupling theory of that phenomenon. When strong finite-system and serial correlation effects made such comparisons extremely tenuous, he developed a finite-system version of the mode-coupling theory and demonstrated consistency both quantitatively and convincingly.
His interest in nonequilibrium effects culminated in a 1982 paper devoted to self-diffusion. That paper established the linearity of the process and fit the many approaches of the preceding 15 years into a remarkably coherent account.
In 1981, Bill left Los Alamos to teach physics at Carroll College in Helena, Montana. He returned to Los Alamos in 1991, where he continued research on pseudo-random number theory and the mode-coupling theory of mixtures, and acted as a consultant in the theoretical division.
Following the 2003 death of his wife, BJ, Bill entered Holy Apostles Seminary in Cromwell, Connecticut, in 2004 to study for the Roman Catholic priesthood. Sadly, his deteriorating health prevented him from completing that lifelong dream.
