Short biography of Hans G.A. Hellmann (1903-1938)

Hans Gustav Adolf Hellmann, one of the pioneers of quantum chemistry, was born in Wilhelmshaven, a harbor town of northwestern Germany, on the 14^th of October, 1903. He studied physics in the post world war I period, from 1922-1929, for most of the time in Stuttgart. Among his teachers were Kossel and Ewald. As a student in Kiel he performed an experimental study of complex dielectric coefficients of ionic solutions, thereby verifying a prediction of the Debye-Hückel-Onsager-Falkenhagen theory. His master thesis on radioactive materials was supervised in Berlin by Otto Hahn and Lise Meitner. At the age of 25 he graduated as a Dr.-Ing. with an experimental investigation of the decay of ozone. In the home of his Ph.D. advisor, Prof. Regener, lived at that time an attractive orphan of Jewish-Ukrainian origin, Victoria Bernstein. Hans Hellmann courted and married her, and just on Hans Hellmann's birthday, Oct. 14, 1929, their son, Hans Hellmann jr. was born.

In the same year, 1929, Hans Hellmann obtained a postdoctoral fellowship at the Hannover Institute of Technology. With the professors Biltz, Klemm and Fischer, chemistry was strongly represented there, and the world center of quantum physics of the time, Göttingen, was only 100 km to the south. Hellmann’s interest turned to the quantum mechanical interpretation of chemical bonding and molecular structure. Initially he refuted - on the basis of the Dirac equation - the speculation that the spin is only an apparent property of bound electrons. Then he developed, already in 1933, the "diatomics in molecules" approach, and solved several open questions, for instance concerning the geometric structure of HN₃. In the same year he published, in an important paper (Z. Physik 1933, 85:180), the molecular virial theorem (a little earlier than Slater) and the force theorem, which later became known as the Hellmann-Feynman theorem. He applied these concepts to the elucidation of the physical nature of the chemical bond, thereby anticipating some of the ideas later promulgated by Ruedenberg. Together with the young physical chemist W. Jost, Hellmann tried (Z. Elektrochemie 1934, 40:806) to communicate the basic ideas of quantum chemistry (a phrase coined by the Austrian physicist A. Haas in 1929) and of chemical bonding to the general chemistry community. His application to "habilitate" with the scientific contributions above was refused and he was fired from his post as an assistant professor on Dec. 24, 1933; he had become undesired, because his wife was Jewish.

Due to the origin of his wife and his political inclination, he had already tried before to gain a scientific position in the Soviet Union. Now he was offered and took the opportunity to move into a leading position at the Karpov State Institute of Physical Chemistry in Moscow. There he finished in 1934 the first paper on the pseudopotential approach (under the title of the "Kombiniertes Näherungsverfahren"), one year before Gombás or 15 years before Phillips and Kleinman. He developed and applied the pseudopotential approach to molecules and solids and published his results in Russian journals, dominantly in German. Two short communications also appeared in English (J. Chem. Phys. 1935, 3:61 and 1936, 4:324). He also worked on other topics such as electrostatic and dispersion interactions, and on elementary diabatic and adiabatic reactions. He continued writing articles for the "ordinary chemist" and even for the scientifically interested laymen, in the Russian language. And he completed the manuscript on the first text-book of Quantum Chemistry, which he had already begun in Hannover. Early 1937 the "Kvantovaja Khimija" came out in Moscow, two years after Pauling and Wilson's "Introduction to Quantum Mechanics" and Van Vleck and Sherman's review of"Quantum Theory of Valence", and three years before Pauling's "Nature of the Chemical Bond". A revised and more compact edition of Hellmann's book in German "Einführung in die Quantenchemie" was finally published at the end of 1937 in pre-Nazi Vienna. During the "Great Terror" of 1937/38 in the Soviet Union (S. Courtois et al.: The black book of communism, Harvard 1999) Hans Hellmann was liquidated at the age of 34 on May 29, 1938. His son, Dipl.-Ing. Hans Hellmann, was permitted to leave Russia not earlier than 1991 and lives now in Siegen, Germany.

An extended bio- and bibliography of Hellmann in German has appeared in Bunsen-Magazin 1999 (ISSN 0005-9021) 1:10-21 and 2:60-70). Reprints may be ordered from schwarz@chemie.uni-siegen.de. An English translation is also available.

W.H.E. Schwarz und J. Hinze