Barry I. Schneider, a physicist in the Applied and Computational Mathematics Division of NIST, passed away at home in Sterling, Virginia, on 3 July 2024, at the age of 83. Although he had struggled with serious medical issues for several years, his passing was nevertheless a shock, as he was an active and vibrant staff member right until the end, taking meetings from his hospital bed and working hard to meet deadlines.
Born in Brooklyn, New York, and educated in the New York public school system, Barry went on to receive a BS in chemistry from Brooklyn College, an MS in chemistry from Yale University, and a PhD in theoretical chemistry from the University of Chicago. Barry went on to become a giant in the field of atomic, molecular, and optical physics over the course of three separate but highly successful and impactful careers.
After a few years at GTE Laboratories in Bayside, Queens, New York, where he used his expertise in collision physics to provide a better understanding of lighting devices, Barry joined the Los Alamos Scientific Laboratory in 1972. There he worked in the Theory Division, contributing his expertise in theoretical atomic and molecular physics to the laser fusion and isotope separation programs. It was there that he realized the potential impact that advances in computational capability would have in the field of atomic, molecular, and optical physics. He worked to develop the needed skills in high-performance computing and applied them to what were until then intractable problems in the scattering and photoionization of molecular systems. He went on to develop three approaches to electron-molecule scattering and photoionization: the R-matrix method, the linear algebraic method, and the complex Kohn variational method. It is fair to say that without combining the skills of quantum chemistry, numerical analysis, and advanced computation, the advances made during that period would not have been possible.
Barry left Los Alamos in 1991 to become the program director for theoretical atomic and molecular physics at NSF in Washington, DC. The awardees in the program included the most outstanding scholars in the field, who were constantly pushing the boundary in sub-areas from cold-atom physics to strong-field laser interactions with atoms and molecules. The Institute for Theoretical Atomic and Molecular Physics, the primary center for theoretical AMO physics in the US, was also included in his portfolio of responsibility. But the program did not focus only on funding for established researchers; it was also the starting point for junior scientists who later went on to establish their own careers in the field. Thus, to a great extent, this program served and continues to serve as a vortex for much of theoretical AMO physics activity in the country.
Barry also served as program director for the NSF plasma physics program, which has both theoretical and experimental components. Basic plasma physics, as taught in universities, was at the time an area that had become noticeably neglected. In an attempt to address the need for improved preparation of future plasma physicists, NSF and the Department of Energy Office of Fusion Energy Sciences began a joint effort that would reach out to reinvigorate the field as an academic discipline. Barry worked closely with the DOE program officer in charge and with other interested units at NSF to establish the partnership. He then, together with DOE, co-led the first competition in 1997. The partnership became the centerpiece of the basic plasma science effort, widely praised and appreciated by the community. It is also to their credit that the partnership continues to exist to this day, a rare example of a long-lasting, successful joint agency effort.
Perhaps the most significant single achievement in Schneider’s tenure at NSF began in 2009 when he left the physics division for the NSF Office of Cyberinfrastructure. There he was responsible for shaping and then managing what became the Extreme Science and Engineering Discovery Environment (XSEDE) program. That program represented a sea change in the way NSF was to manage its supercomputer programs. What was originally a group of five essentially independent and fiercely competitive centers became a more coherent and centrally managed but geographically separated (virtual) program. XSEDE was hugely successful, providing high-quality research computing to the community over a period of 10 years.
While at NSF, Barry also spent time as a guest researcher in the NIST Physics Laboratory in nearby Gaithersburg, Maryland, working with NIST researchers modeling the creation of solitons and vortices in Bose–Einstein condensates. One of those papers has been cited 1680 times. Barry joined NIST on a full-time basis in 2014 to serve as the General Editor of the NIST Digital Library of Mathematical Functions project.
At NIST, Barry also continued his work in computational physics, working with many collaborators to develop techniques and software to treat polyatomic molecules exposed to attosecond radiation. It is noteworthy that the 2023 Nobel Prize in Physics was given for the creation of extremely short pulses of light that can be used to capture and study rapid processes inside atoms. It is just these processes that Barry was studying. In fact, a paper Barry coauthored is cited in the technical document describing the Nobel Prize–winning work.
Unhappy with the state of software sharing in the atomic, molecular, and optics research community, Barry was the visionary behind the development of what has become the AMOS Gateway, an online portal for research and education in atomic, molecular, and optical science (AMOS). By removing major barriers to coordination and creating a comprehensive cyberinfrastructure where AMOS practitioners can access a synergistic, full-scope platform for computational AMOS, the gateway provides the entire AMOS community with state-of-the-art tools to perform cutting-edge research. It also serves to educate students in AMOS science at both the undergraduate and graduate levels.
In recent years, Barry was also a driving force in the movement to improve NIST’s internal infrastructure for performing computational science, an effort that had just begun to bear fruit at the time of his passing. NIST scientists will benefit from that legacy for a long time.
Among the distinctions Barry received over the course of his career were the Poste Rouge of CNRS from the French government (1980), American Physical Society (APS) Fellow (1982), the Senior Humboldt Prize of the German government (1987–88), and the Department of Commerce Bronze Medal (2020). During 2004–05, Barry served as Chair of the APS Division of Computational Physics. He is the author of some 140 refereed papers and books. He also served as co-chair of the NITRD High Performance Computing Working Group (2018–20) and was recently co-chair of the US government Fast Track Action Committee tasked to update the US strategic computing plan. For many years, he served as an associate editor for IEEE Computers in Science and Engineering magazine and as a specialist editor for Computer Physics Communications.
On a personal level, Barry was extremely outgoing. He loved people and loved to talk. (Getting the last word in an email back-and-forth with Barry was simply impossible.) He was generous in sharing stories about his long career. He loved music and led a rock-blues band all through college. He claimed not to be a very good musician, but he admitted that he sang well. He admired good guitar playing, the likes of Chet Atkins, Tommy and Danny Gatton. But Barry also loved opera and shared many happy conversations with like-minded people at NIST. The Italian tenor Franco Corelli was one of his favorites. Barry was also a serious runner before a heart condition prevented him to continue. His father had passed in his 50s of heart problems, so he worked hard to reverse that in himself through diet and exercise.
Barry also was a great mentor. In his final years at NIST, he supervised two postdocs, a graduate student, and several undergraduates, all of whom were very successful. Barry was also generous with his time. Whenever someone was needed to perform some special task for the laboratory or the division, Barry was there. We do not know how he had the time to do everything he did. But he loved his work, loved NIST, and was technically active up to a few days before his passing. We are grateful for that and are grateful for what he has given us. As an undisputed giant in the field of computational physics, Barry’s passing has left a big gap, but his legacy is everywhere.
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