Walter Thiel

Prof. Walter Thiel passed away unexpectedly on August 23, 2019.

Walter Thiel’s passing comes as a big shock to all of us, to his family, friends, and colleagues all over the world. This is a great loss to the whole scientific community.

For me, Walter was not only great boss, mentor, but also a very close friend. He helped me on many occasions including difficult personal situations. I will always remain in debt to this great man.

Walter was a very kind person and I was not the only one, whom he helped through difficult times. I know many touching stories, when Walter boundlessly supported his students/post-docs, when their life was breaking apart.

Walter treated everyone with utter respect as equals and nurtured independent scientific thinking in each of us, his students. He was never micromanaging and everybody was free to use their time as they wanted. He encouraged independent work. No wonder that so many his former students/post-docs/group leaders in his department built successful independent careers. I will just mention a few of them with whom I most overlapped during my stay in Max-Planck-Institut für Kohlenforschung, where Prof. Thiel was the director of Theoretical Chemistry department since 1999 until recently. Mario Barbatti was an independent group leader in Walter’s department in 2010-2015 and is now a professor in Marseille and recent ERC Advanced Grant awardee. Guijuan Cheng was Walter’s post-doc in 2015-2017 and is now a professor in Hong Kong. Matthias Heyden was an independent group leader in Walter’s department in 2014-2017 and is now a professor in Arizona. Elsa Sánchez-García was Walter’s post-doc and later group leader and now is a professor in Essen.

Walter had a knack for choosing good people for his department. We all became close friends and have warm, friendly, respectful relationships, albeit we may have sometimes vigorous discussions on many topics.

It was a great honor for me to be his very last post-doc. I applied to Walter for a post-doc position in 2013 and my first impression from seeing his photo was that he was a very kind person. This proved true. He invited me to give a talk in a seminar, which was kind of a job interview. I remember how deeply impressed I was by the quality of questions from his department members, which showed the high class of these specialists. After my talk, Walter offered me the job and told me that I would have enough freedom to pursue my own independent research interests. That’s how I could do my machine learning research and publish half of my papers independently of Walter Thiel while being his post-doc. Trust in his students was what made Walter such a great supervisor.

For me as well as for many of our community, Walter Thiel’s name is most strongly associated with semiempirical quantum chemical method development, particularly with MNDO, which gave rise to so many other semiempirical methods (AM1, PM6, PM7, OMx…), although Walter Thiel’s interests reached much further and he made great contributions to so many other fields (QM/MM, spectroscopy, photochemistry, catalysis…). I would argue that semiemprical methods and his own program he developed from his time as a post-doc with Dewar remained his greatest passion after his official retirement. He built many plans for them, which he shared with me as his last student, who works on semiempirical method development. We planned to continue to work on so many things together after my eventual leave to an independent position this September.

I learned a lot from Walter, he knew so much and was so efficient… I owe him a lot. Now it is my responsibility to finish many research projects we started with him to honor his work. I will miss greatly our discussions, his attention to every single detail, and his wise advise. I will miss his humor, our informal communications when we talked on so many topics as we shared so many interests. I will always regret that we have never played a single game of chess, the game we both loved so much, but were always too busy to play…

Walter Thiel may have passed away, but his legacy will leave forever through his outstanding scientific contributions and his grateful students.