TASQ Open seminar

I was born on the 26th of March 1958 in Malmö, Sweden. For the first part of my life there was not much that hinted at a scientific career; however, at an early age I was keen on mathematics. Additionally, while being home sick from school in the 60s, I watched “Skol-TV” (School Television) which broadcast their program before noon on the only state TV channel available in Sweden at that time. Specifically, the program, which had an older white-haired gentleman in a white lab coat explaining chemistry, was inspirational. In particular, the animated movie on how table salt is dissolved in water into sodium and chlorine ions was to me both mind-boggling and fantastic. Later in life I developed both my skills in math and the fascination for chemistry. Already in high school (gymnasium)─the first two years in Kristianstad and later in Malmö─I attended the four-year technical education program in chemistry. Here I’m eternally grateful to the math teacher who forced the students to use a programmable HP hand-held calculator with reverse Polish notation over the Texas Instrument alternative─this was fundamental in shaping my mind in how to relate to and process data. Moreover, during the third year of the program was the first time I ever encountered a computer (a bulky HP stationary desk computer). With much eagerness, manuals were read and the first computer codes of mine were developed.

After a mandatory 15 months of military service, I enrolled in 1979 at Lund’s institute of Technology (LTH) at Lund University (LU) to study for a degree in chemical engineering. Of the mandatory classes, the one in coding with the Fortran 77 program language was the one that had the greatest resonance with me. My third-year research project involved an animation of a lithium ion in water (24 water molecules) based on molecular dynamics trajectories, using an analog camera, computer generated pictures, and stop-motion technique. At this instance in my life, it was the first time I was exposed to the notion of becoming a Ph.D. student and devoting my adult life to science─how interesting! Ushered forward by my wife, Marie-Louise, 1982–83 was spent together as exchange students at University of California, Los Angeles. It was where I published my first scientific publication as a minor contributor to a manuscript from the research group of Charles Knobler─thank you. Back in Sweden again, I graduated with a master’s in technology (a civil engineering degree) in 1983.

In the fall of 1983, I enrolled in the Ph.D. program at the Department of Physical Chemistry 2, at LU. The plan was to work in the field of statistical and molecular mechanics; however, those plans were altered after a short while and my affiliation was changed to the newly formed Department of Theoretical Chemistry under the leadership of Prof. Björn O. Roos, who also became my Ph.D. advisor. The research involved both theory developments and computer implementations; here I could merge my skills for math with my passion for chemistry, computers, and coding. Much of these developments were under the influence and inspiration of Per Åke Malmqvist’s protection, mentorship, and excellent scientific and mathematical skills.

This was followed by a postdoc stint at the IBM Almaden Research Center in San Jose, CA, where I joined the group of Bowen Liu. For a two and a half year stay, I had the opportunity to work with some of the most prominent scientists in this field─some of them stationed at NASA Ames, just up the road from San Jose, some of them older and wiser, some of them my own age─for example, Julia Rice, Alistair Rendell, Les Barnes, and Tim J. Lee. Development projects involved enabling Gaussian 88 for the IBM 3090 main frames and coding contributions to the Hondo program package. It was also here at IBM Almaden where I started to proceed with my first major code development project─the Seward code for the computation of so-called two-electron integrals based on a revitalized version of the Rys–Gauss approach. The code is today still an integral part (no pun intended) of the OpenMolcas quantum chemistry program project.

Repatriated to LU and the group of Prof. Roos in 1991, I was thrown into the new and quickly evolving in-house project of MOLCAS (the historical origin of the OpenMolcas project). In the years that followed, I was a keen developer and advocate of the program project. In this period, techniques and more coding were developed, addressing, for example, analytical gradients and Hessians, and molecular structure optimizations─this together with my first two Ph.D. students Anders Bernhardsson and Jonna Stålring. This was when I was also forging friendships with peers and postdocs at LU, such as Martin Schütz, Jeppe Olsen, and Dage Sundholm. The Seward code opened also the basis for international collaborations with the Molpro group, under the leadership of Hans-Joachim Werner, and the ACES 2 project in Gainsville, Florida, led by Prof. Rod Bartlett. With my transfer in 1997 to the Department of Chemical Physics, under the leadership of Prof. Villy Sundström, I developed an interest in femtosecond laser spectroscopy; since then, much of my theory developments and computer implementations have revolved around these experimental methods. A longer stay in Kimihiko Hirao’s research group at Tokyo University in 1998 both was inspirational and allowed for hard work on parallelization of several of the integral basis implementations. This was followed by longer stays in Tokyo for years to come, during which my family and I had the chance to develop our taste for Japanese cuisine. In 2003, I was promoted to the rank of professor at LU. In 2007 I was transferred back to the Department of Theoretical Chemistry, where I explored my interest and fascination in chemi- and bioluminescence. This was experienced together with Luca De Vico, Fengyi Liu, Nicholas Ferré, Yan-Ju Liu, and Isabelle Navizet, which resulted later on in extensive stays in Marseilles, France, Beijing, China, and Paris, France. This collaboration eventually led to a publication in 2018 in Chemical Reviews on the principles of the phenomena, something I am very proud of. At the same time, I also, in collaboration with Francesco Aquilante and Thomas B. Pedersen, both at LU at that time, started a very productive project on Cholesky decomposition of two-electron integrals and the resolution-of-the-identity approximation of the very same two-electron integrals. Since 2009, I have been the chair of the MOLCAS project. A stray phone call in 2008 to Markus Reiher at ETH, Zürich, to sort out the issue of the so-called picture-change effect has resulted in a long fruitful collaboration on the relativistic effects in Mössbauer spectroscopy, but subsequently also on other matters as, for example, the implementations of the density matrix renormalization group approach of the complete active space approach in MOLCAS.

In 2010, I moved to Uppsala University (UU) and held there the chair in theoretical chemistry until 2018─big shoes to fill. During this time, I had the good fortune to have excellent Ph.D. students and postdocs─for example, Mickaël Delcy, Mickael Stenrup, Lasse Kragh Sørensen, Daniel Sethio, Henrik Stegeby, Danjo De Chavez, Mihkel Ugandi, Daniel Roca Sanjuán, and Stefano Battaglia. It was also here I started my long and prosperous collaboration with Ignacio Fdez. Galván, who is still to this day working with me at UU. Since, 2012, I have served as the chairman for the committee for the so-called Löwdin lectures, a very rewarding work. In May 2013, I was elected a member of the Swedish Royal Society of Science. At UU I have continued working on developing several projects, for example, the MOLCAS project, which today has metamorphized into the international OpenMolcas open-source program project, the further development of techniques to simulate molecular systems under the influence of X-ray radiation, additional improvements of numerical quadrature methods and fast integral methods, and further improvements of the CASPT2 method.

In 2017 I did an 8-month sabbatical stay in Alán Aspuru-Guzik’s group at Harvard, Cambridge, USA. This was an eye-opening experience with respect to the uncharted territories of the usefulness of machine learning and artificial intelligence techniques in quantum chemistry. These techniques will fundamentally change how chemistry and theoretical chemistry will proceed into the future and what the goals of chemistry research will be. This is something I am very happy to have expressed in the paper entitled “The Matter Simulation (R)evolution”, penned together with Alán and Markus.

During my career I have enjoyed the close collaboration with many scientists, which has led me to many interesting places all over the world and enabled me to forge friendships that will last for the rest of my life. For this I am very grateful. Thank you all!