Special Issue Preface pubs.acs.org/JPCA
Autobiography of Lawrence B. Harding first Floating Point Systems Attached Processors to provide for our computational needs. With Ron’s electronic structure codes running on our own FPS/164, it became possible to survey potential energy surfaces at a level of accuracy and detail that simply had not been possible before. I feel very lucky to have been in the right place at the right time to take advantage of state-of-the-art advances in both electronic structure theory and computer hardware. For quite a while our abilities to fit, multidimensional, potential energy surfaces lagged behind our abilities to do large numbers of accurate electronic structure calculations. During this time George Schatz and I collaborated on a number of different surface fitting projects, including H + CO2, OH + CO, CN + H2, and CH2. These involved tedious, trial and error attempts to fit the important parts of the surface with various simple, functional forms. Fortunately, George was a master at this. Also during this time I fit what has become known as the BBH surface for HCO using a Shepard-type interpolation method followed by a three-dimensional spline to improve the computational efficiency. In 1984 I met Jürgen Troe at the International Combustion Symposium in Ann Arbor. This led to a series of collaborations on H + O2 and O + NO combining my electronic structure calculations with Jürgen’s Statistical Adiabatic Channel Model. In the mid-1980s the Theoretical Chemistry Group at Argonne was transformed into the Gas Phase Chemical Dynamics Group by the addition of experimentalists including, Kopin Liu, Glen Macdonald, Jan Hessler, and Joe Michael. John Kiefer also became a regular visitor. Later Branko Ruscic, Steve Pratt, Rob Tranter, and Raghu Sivaramakrishnan joined the group. The proximity of these experimentalists led to a large number of theory/experiment collaborations. A good example of these collaborations was our re-evaluation of the enthalpy of formation of the OH radical in which a team of experimentalists and theorists, led by Branko Ruscic, demonstrated that the then accepted enthalpy of formation was in error by 0.5 kcal/mol. In 1992/1993 I spent a year as a visiting fellow at JILA. Although I enjoyed the stay in Boulder immensely, hiking or skiing most weekends, it was a frustrating time scientifically. I spent much of that year fruitlessly looking for a pathway by which the reaction of CH3 with oxygen atoms could produce CO, as suggested by experiments done in Steve Leone’s laboratory. The answer to this puzzle did not come until several years later when Stephen Klippenstein and I, using direct dynamics methods, found that CH3O can decompose to HCO + H2 via a non-IRC process. One project that stayed on the backburner for many years was to understand the bimodal product state distributions observed by Brad Moore in the photodecomposition of formaldehyde. The reason for the delay is we felt this must be another non-IRC process similar to the decomposition of
I
was born in Princeton, New Jersey, in 1951. I grew up in Geneseo, New York, where my father taught in the English Department at SUNY Geneseo and my mother worked as a RN in the doctor’s office next door to our home. My interest in chemistry began at an early age, setting up a chemistry lab in our basement by the age of ten. This was at a time when chemistry sets designed for children provided significant opportunities for mayhem. Unfortunately, I believe this is no longer true today. Much of my early “work” focused on explosives. I recall making gunpowder by the pound, once accidentally setting off a large batch in the basement, filling the house with dense smoke. Later I moved on to study H2/O2 explosions. Taking apart old flashlight batteries provided a ready source of zinc and manganese dioxide. Hydrogen could then be made by reacting the zinc with hydrochloric acid and oxygen by reacting the manganese dioxide with hydrogen peroxide. My parents used to enjoy telling the story about when I filled a balloon with hydrogen, attached a fuse and floated it over the Memorial Day parade from the roof of our house. Looking back on my childhood it seems a bit surprising that I survived with all body parts intact and no criminal record. I went to Wesleyan University in Connecticut as an undergraduate majoring in chemistry and mathematics. I spent one summer there working in Peter Leermakers’ laboratory on the photochemistry of alkynes. Sadly, Peter Leermakers died in an auto accident that summer. The following summer I made the switch from experiment to theory doing semiempirical calculations on models for ADP and ATP under the guidance of David Todd. In the fall of 1973 I arrived at Cal Tech and quickly decided to join Bill Goddard’s group. My first project there was on the low-lying electronic states of formaldehyde. Little did I realize that this would be the first of about ten papers I would publish on formaldehyde. Early in my stay at Cal Tech, Bill and I published a paper with Jack Beauchamp on the interpretation of the trapped electron spectra of formamide. This would be the first of many enjoyable, collaborative efforts with experimentalists. One of the papers I am most proud of from these Cal Tech years is one titled “The Description of Chemical Bonding from Ab Initio Calculations” in Annual Reviews of Physical Chemistry. In this paper we illustrate the predictive power of simple, qualitative, valence bond concepts derived from ab initio calculations. In the fall of 1978, I left Cal Tech, drove across the country in a U-Haul truck to Pittsburgh, stopping on the way to interview for a position at Argonne National Laboratory. I then spent a much too short year in Pittsburgh working with John Pople as an NSF National Needs Postdoctoral Fellow. After Pittsburgh, I moved to Illinois to join the Theoretical Chemistry Group at Argonne National Laboratory then headed by Thom Dunning. These were exciting times to be at Argonne. Al Wagner had recently joined the group and George Schatz and Joel Bowman would each spend 1 day a week at Argonne. Later on, Ron Shepard, Ray Bair, and Robert Harrison all joined the group and we acquired one of the © 2015 American Chemical Society
Special Issue: 100 Years of Combustion Kinetics at Argonne: A Festschrift for Lawrence B. Harding, Joe V. Michael, and Albert F. Wagner Published: July 16, 2015 7078
DOI: 10.1021/acs.jpca.5b01875 J. Phys. Chem. A 2015, 119, 7078−7079
Special Issue Preface
The Journal of Physical Chemistry A CH3O. This meant that the solution would require trajectories, either via direct dynamics or on an analytic potential energy surface. Both the direct dynamics and the potential surface fitting proved to be challenging. The surface-fitting bottleneck was finally solved by Bastiaan Braams’ development of a new fitting technique involving permutationally invariant polynomials in Morse-type variables. This led to the discovery of what have now come to be called roaming radical reactions. Interestingly, it turns out that these roaming radical reactions are not non-IRC processes and, as Stephen Klippenstein, Yuri Georgievskii, and I have shown, one does not need trajectories on full dimensional potential surfaces to accurately treat these reactions. Had we realized this we could have solved this problem many years earlier. I have worked at Argonne National Laboratory for over 35 years. I would like to thank the Department of Energy, Basic Energy Sciences, for their support over all of these years. I must also thank all of the past and present members of the Gas Phase Chemical Dynamics group to whom I owe much of my professional success. Finally, I would like to thank my wife, Roo, for her support and willingness to put up with too many, seven-day workweeks.
Lawrence B. Harding
7079
DOI: 10.1021/acs.jpca.5b01875 J. Phys. Chem. A 2015, 119, 7078−7079
