Karl Fischer, emeritus professor of crystallography at the Universität des Saarlandes (Saarbrücken), passed away on 29 October 2022 at the age of 97 in active retirement. It was just one year ago, when he had been awarded the prestigious Carl Hermann Medal by the German Society of Crystallography (DGK) for his lifetime achievements in the field of structure research and promotion of national and international cooperation.
Among the latter, using the historical golden opportunity of the political unification process between East and West Germany in 1989/90, Karl Fischer joined actions to build bridges across the disintegrating Iron Curtain, actively bringing together crystallographers from both sides of the former frontier. He acted as representative of the West German Working Group of Crystallographers (AGKr) in various responsibilities, e.g., as member of the board of AGKr and chairman of the West German National Committee for Crystallography. To overcome the separation, the boards of both crystallographic bodies in West and East Germany decided to dissolve their organizations and to restart in 1991 with a common all-German Society of Crystallography (DGK). He became founding member of DGK and was reelected as member of the German National Committee.
Karl Fischer was born 4 July 1925 in Zwickau, Saxony. His father, Emil Fischer, was teacher of mathematics, physics and chemistry with an external PhD degree and keen interest in mineralogy and crystallography. Evidently, his pleasure in science was transmitted to Karl. From June 1944 on Karl served in the military and became involved in the final fights against the Soviet Red Army. In 1945, after the end of World War II, Saxony became part of the Soviet Occupation Zone. Hence, Emil’s status as a public servant was terminated and life of the family experienced an economic decline. After initially finding employment in chemical industry, in 1954 Emil Fischer assumed the position as custos of the (East) Berlin Mineralogical Museum under the leadership of Will Kleber. There, Emil Fischer wrote the popular textbook “Einführung in die geometrische Kristallographie“, which appeared in 1956. At that time, Karl could already have made use of it as prospective tutor.
When, immediately after the war, Karl Fischer was to choose the proper subject for his professional development, he recognized that in the Soviet Zone admission to university for members of the former educated middle class was restricted. Thus, he decided – in accordance with his parents – to leave East Germany to study chemistry at Erlangen University, which at that time belonged to the US Zone. There – under the supervision of Karl Rudolf Andreß – he received his diploma in 1952 and the Dr.phil.nat. degree in 1954. From the very beginning, his attention was drawn to the characterization of crystal structures using X-ray diffraction. His further path led him to the Institute of Mineralogy and Crystallography at the University of Frankfurt/Main, headed by Herbert O’Daniel , where during the period 1955-1964 he set the course for a successful university career. He habilitated in 1962 with a thesis “Refinement of atomic scattering curves and determination or refinement, respectively, of several silicate structures: Gmelinite, Gismondine, Benitoite, Cummingtonite”. Most importantly, in the years 1960-61 his focus in the wide area of X-ray diffraction sharpened on the atomic form factor, when he was invited to a research fellowship in the group of Martin J. Buerger at MIT, Cambridge/Mass.
Being appointed as professor of crystallography in 1964 at the Mineralogical Institute of Saarland University (director Franz Rost), Karl Fischer started a fruitful period in crystal structure research lasting long beyond the year of his retirement, 1993. In particular, he took advantage of the advent of synchrotron radiation (SR), as DESY/Hamburg had just become operational in 1964. Since originally this newly established facility was not intended to become a light source but an instrument to solve problems of particle science instead, it was both a challenge and an opportunity to open access to a new quality of X-ray scattering studies. Early on, Karl Fischer made use of the extraordinary features offered by SR for the study of anomalous scattering, such as polarization, tunable wavelength and high intensity. Together with Ulrich Bonse, Hans-Georg Krane and Wolfgang Morgenroth he designed new instruments to exploit these features. The first results could be published in 1981, when by opening the Hamburg Synchrotron Laboratory (HASYLAB) an example was set for the significance of SR. Under the catch word ‘anomalous scattering’ a number of pioneering studies done by Karl Fischer and his group provided deeper insight into the impact of individual atoms upon physical properties of materials. Fruitful collaboration with Armin Kirfel stimulated further applications.
During the past twenty-odd years Karl Fischer pursued the idea of an alternative method to solve structures without Fourier transform. He did so, up to the age of 97, in attending weekly online-discussion rounds about that topic. These approaches which he coined ‘Parameter Space Concepts’ are still subject of research supported by the German Research Foundation (DFG). The first results had been published in 1998 together with his PhD student Katrin Pilz, a crystallographer from Leipzig University. Then, he received essential support by Armin Kirfel and Helmuth Zimmermann, who co-authored several related publications. Based on his ideas and enduring advise, the concepts are being more and more refined by a group at Technical University Bergakademie Freiberg headed by Dirk C. Meyer. The scientist responsible for the project, Matthias Zschornak (recipient of the Ninth Erwin Felix Levy Bertaut Prize of ECA), had been in close contact with Karl Fischer until recently. In a sense, that way Fischer’s heritage will be maintained in Saxony, where he grew up.
The expertise in structure research, his engagement for so called ‘small disciplines’ and, particularly, his altruism earned Karl Fischer great and lasting recognition among colleagues. Therefore, he was elected for peer review of research grant applications to the DFG, the German Federal Ministry of Research and Technology (BMFT) and the Institut Laue-Langevin (ILL). Numerous researchers benefitted from his fair assessments and time-consuming engagement.
We are mourning for Karl Fischer, an inspiring scientist and esteemed representative of our science and kind colleague. His family and friends have our deepest sympathy for the loss.
Peter Paufler (Dresden), Dirk C. Meyer (Freiberg)
P.S. Details of his curriculum vitae and a list of publications may be found in “Mitteilungen der Deutschen Gesellschaft für Kristallographie 51(2021)63-74” (in German).