Personal foreword: John Stanton special issue

In 1986, I was very fortunate to receive a Guggenheim Fellowship that I used to spend a semester at Harvard in the group of W. N. Lipscomb, known to all as the ‘Colonel’ because of his honorary Kentucky Colonel status. In his group, he had a new graduate student, John Stanton. The Colonel primarily did X-ray crystallography for proteins but had always had a theory component to his efforts over the years that was the attraction for me. He appreciated the MBPT and coupled-cluster theory my group was doing, and how accurate our results were for molecules like diborane and related BH 3 containing species. As I recall, John was not sure at this point whether he would do experiments or theory, but he was anxious to learn many-body theory and I was glad to present some lectures about diagrammatic methods, linked diagrams, size-extensivity, and the infinite-order summations of MBPT offered by coupled-cluster theory. As anyone that knows John is aware, he is a very quick study, and he rapidly mastered all these tools. This enabled us to establish a fruitful collaboration: Lipscomb picked the molecules, I supplied the aces i program that had many features and methods unique to quantum chemistry at the time, and John made the calculations. The results of this effort led to 11 jointly authored papers published between 1987 and 1989, all originating with that one semester visit to Harvard. The subjects were diborane, beryllium borohydride, BH 5, triborane, augmented by a more methodological study of O 3 that warranted three papers, itself. Another paper dealt with IR intensities and the early stages of diborane pyrolysis. I mention these two, in particular, as two critical components of John's current work is kinetics and his in-depth tie to high resolution spectroscopy. These were the first efforts along that path.

John joined me as a postdoc in 1991, where the next stage in his impressive work was accomplished. After tiring of the limitations in aces i, he took it upon himself, later assisted by Juergen Gauss and John Wattts, to write aces ii, a complete re-write of the CC program, its gradient code, and EOM-CC to employ Abelian symmetry. Like spectroscopists, John recognised the advantages of symmetry for detailed studies of small molecules, one of his prime objectives in life, but other CC/MBPT programs (as opposed to CI) were not written to include symmetry. Their work enabled aces ii to give a factor of 64 improvement in a CCSD calculation for a D${}_{2h}$ molecule. This formal advance was termed ‘Direct Product Decomposition’, and their equations are often followed today by those who write new CC programs.

Just as he was exceptionally productive while still a graduate student, he published 10 quality papers in 1991, including his first foray into the NO₃ molecule, a long-term interest of John's. In 1992 he added 11 more. In 1993, before he moved to Texas, he added three more, one of which is our most highly cited joint paper on EOM-CC. We had been playing with this idea since 1984, but it only achieved full generality in John's hands. Another paper by John showed for the first time how one could use EOM-CC eigenvectors to calculate the dynamic polarisability of a molecule. Later work by Perera et al. further amplified on the rigorous treatment of second-order properties in CC theory building upon this start. Our final effort, “Applications of post-Hartree Fock Methods: A Tutorial,” in Reviews in Computational Chemistry, 1994, offered a mini-textbook on the subject

John's many, notable contributions after leaving my group should be told by the authors of the papers in this special issue. It is, indeed, an impressive array of authors who can best appreciate the exceptional quality of his work. We at QTP, are fortunate to once again have him with us as our Kenan Professor!

Disclosure statement

No potential conflict of interest was reported by the author(s).