Hans Hellmann: Life Story of a Scientist in the 20th Century

Abstract

This communication consists of three parts: (i) biography of Hans Hellmann, a real pioneer in quantum chemistry, (ii) Hellmann´s achievements, and (iii) reflections on the mankind destiny in the 20th century. When the Nazis seized power in Germany in 1933, Hellmann realized that emigration became a necessity for his family. In 1934-1937 he worked at the Karpov Institute in Moscow; he was imprisoned in 1938 and a few weeks later executed by the Soviet secret service. Hans Hellmann (1903-1938) was not only a brilliant theoretical physicist but also a man who was able to perfectly define experiments and carry them out, a physicist with real and deep feeling for chemistry and, particularly, a man with a remarkable vision. Hellmann´s notable achievements are briefly reviewed and their impact on contemporary chemistry is emphasized. Attempt has been made to create a collage on the basis of six Hellmann´s scientific masterpieces which could be suitable for inclusion in a Hall of Fame. The first deals with the Hellmann-Feyman theorem that has played a prominent role in molecular geometry gradient optimization. The next one is associated with pseudopotentials, which have made possible the entry of quantum chemical treatment into the area of heavier atoms. The third achievement concerns non-covalent bonds, which assume a key position in the description of condensed matter and are essential in the whole realm of biodisciplines. The virial theorem, the fourth success, has played a great role in understanding the nature of the chemical bond. Hellmann´s experimental abilities have been documented by his measurements of frequency-dependent dielectric permittivity, ozone decomposition in stratosphere, and chemical reactivity. The last achievement is his extensive work Quantum Chemistry (in Russian), published in 1937, which is still an impressive textbook. In the final section, the transitions of the mankind from the Age of Reason to democracies and also extremely brutal dictatorships of the 20th century are briefly outlined; this is a good frame of the Hellmann's life story. Another feature of that century is unparalleled expansion and development of science and technology, quantum mechanics being the greatest scientific achievement of that century. The paper is closed by a quotation from G. Santayana: "Who does not remember the past, is condemned to repeat it". The author believes that it is the moral obligation of seniors in science to regularly remind junior scientists of this sage observation.