Clemens CJ Roothaan

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Clemens CJ Roothaan (born August 29, 1918 in Nijmegen ; † June 17, 2019 ) was a Dutch physicist , chemist and computer architect.

life and work

He enrolled in 1935 at the TU Delft to study electrical engineering , and studied at times at the University of Karlsruhe . He listens to lectures by Hendrik Anthony Kramers and Ralph Kronig , among others . During the Second World War and the occupation of the Netherlands, he and his brother were initially imprisoned for aiding and abetting resistance to the occupation , and later they were taken to a concentration camp in Vught , the Netherlands . While in captivity, he was able to continue his studies in physics with other interned professors and students under the formal guidance of Philips . The camp inmates were transferred to the Sachsenhausen concentration camp near Oranienburg on September 5, 1944 because of the approaching Allied associations , where Roothaan became part of a construction team. On April 20 of the following year, he and the surviving inmates were forced to go on a death march towards the Baltic Sea , which however disbanded 12 days later at Schwerin . His brother did not survive the concentration camps.

The final report of his training at the provisional “university” in the concentration camp, which was sent to Philips headquarters, was recognized by the TU Delft on October 14, 1945 to enable him to acquire an engineering degree. In January 1946, Roothaan moved to the United States on a scholarship at the University of Chicago . At that time Chicago was one of the focal points of physics with professors like Enrico Fermi , Edward Teller , Maria Goeppert-Mayer , Robert Mulliken , James Franck and Leó Szilárd . Since he was excluded from the nuclear physics programs as a foreigner, he turned to quantum chemistry and began a doctoral thesis with Robert S. Mulliken. His research topic was calculations on benzenes based on semiempirical molecular orbital theory . He realized that the approach used at the time was formally wrong and changed his approach, which then led to the development of the Roothaan equations , which became fundamental in quantum chemistry (see chemical bond ) and a Hartree-Fock method with non-orthogonal Basic functions are. They are also sometimes called Roothaan-Hall equations after George G. Hall , who found them independent in 1951 . Roothaan's publication was one of the most cited works of the time. Mulliken mentions Roothaan's work in his Nobel Lecture (1966) as follows:

“I tried to induce Roothaan to do his Ph.D. thesis on Hückel-type calculations on substituted benzenes. But after carrying out some very good calculations on these he revolted against the Hückel method, threw his excellent calculations out the window, and for his thesis developed entirely independently his now well-known all-electron LCAO SCF self-consistent-field method for the calculation of atomic and molecular wave functions, now appropriately referred to, I believe, as the Hartree-Fock-Roothaan method. ”

“I tried to get Roothaan to base his doctoral thesis on calculations of substituted benzenes using the Hückel method . But after some very good calculations, he began to revolt against the Hückel method, threw his excellent calculations out the window, and finally developed his now well-known all-electron LCAO -SCF self-consistent field method for his doctoral thesis for his doctoral thesis molecular wave functions, now appropriately referred to as, I believe, the Hartree-Fock-Roothaan method. "

During his doctoral thesis Roothaan was employed by Karl Ferdinand Herzfeld at the Catholic University of America in Washington, DC (on the mediation of Maria Goeppert-Mayer). In 1949 he got a job at the University of Chicago , and received his doctorate in 1950. He then devoted a considerable part of his time to the numerical calculation of molecular orbitals, based on his LCAO-SCF method (SCF for Self Consistent Field). He became an instructor in physics and chemistry in Chicago in 1950, was professor of communications and computer science from 1965 to 1968, and from 1962 to 1968 he was director of the University of Chicago Computation Center, and then professor of physics and chemistry at the University of Chicago ( Louis Block Professor ). In the 1960s and 1970s, he and his colleagues undertook extensive computer calculations on quantum chemistry. In the 1970s he and his student John Detrich led the way in the development of efficient multi-configuration computations of self-consistent fields (MCSCF). As early as the 1960s, he was a consultant at IBM in supercomputer developments.

After retiring in 1988, he worked for Hewlett-Packard Laboratories in Palo Alto , California , where his major contributions were in the development of the math coprocessor routines for the Itanium chip suite. His method of analyzing pipeline architectures was unique and innovative and is highly valued in supercomputer circles.

He was a member of the International Academy of Quantum Molecular Science , a member of the American Physical Society , a corresponding member of the Dutch Academy of Sciences and an honorary member of the Gelato Foundation . In 1957 he was a Guggenheim Fellow at Cambridge University. 1958 to 1966 he was a consultant to the Argonne National Laboratory , 1960 to 1965 a consultant to Lockheed , from 1965 to Union Carbide and IBM . He was visiting professor at Ohio State University (1976) and at the TU Lyngby (1983).

literature

  • Clemens CJ Roothaan: My life as a physicist: memories and perspectives . In: Journal of Molecular Structure: THEOCHEM . tape 234 , September 20, 1991, pp. 1-12 , doi : 10.1016 / 0166-1280 (91) 89002-I ( online ).

Individual evidence

  1. ↑ International Academy of Quantum Molecular Science . Retrieved August 7, 2013.
  2. ↑ News & Announcements June 19, 2019 ufl.edu, accessed on June 26, 2019
  3. ↑ Kostas Gavroglu, Ana Simoes Neither physics nor chemistry- a history of quantum chemistry , MIT Press 2012, p. 220, biography of Roothan
  4. ↑ Rothaan New Developments in Molecular Orbital Theory , Reviews of Modern Physics 23, 1951, 69-89
  5. ^ GG Hall: The Molecular Orbital Theory of Chemical Valency. VIII. A Method of Calculating Ionization Potentials . In: Proceedings of the Royal Society A . tape 205 , no. 1083 , March 7, 1951, p. 541-552 , doi : 10.1098 / rspa.1951.0048 .
  6. ↑ Biography of Roothaan in Don Shillady Essentials of Physical Chemistry , CRC Press, 2012 p 452
  7. ^ Nobelprize.org: Nobel Lecture: Spectroscopy, Molecular Orbitals, and Chemical Bonding (PDF; 285 kB), December 12, 1966.
  8. ↑ Roothaan, Detrich, Darrel G. Hopper An improved MCSCF method , Int. J. Quantum Chemistry, 16, Issue Supplement p. 13, March 1979, pp. 93-101
  9. ↑ Reflections on My Fifty Year Involvement with Computers (Memoirs of Roothaan's student Irving Wladawsky-Berger)
personal data
SURNAME Roothaan, Clemens CJ
BRIEF DESCRIPTION Dutch physicist, chemist and computer architect
DATE OF BIRTH August 29, 1918
PLACE OF BIRTH Nijmegen
DATE OF DEATH 17th June 2019