Clemens C. J. Roothaan (August 29, 1918 – June 17, 2019) was a Dutch physicist and chemist known for his development of the self-consistent field theory of molecular structure.

Biography

Roothaan was born in

Nijmegen Nijmegen (;; Spanish and it, Nimega. Nijmeegs: ''Nimwèège'' ) is the largest city in the Dutch province of Gelderland and tenth largest of the Netherlands as a whole, located on the Waal river close to the German border. It is about 6 ...

. He enrolled

TU Delft Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...

in 1935 to study

electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

. During World War II he was first detained in a prisoner of war camp. Later he and his brother were sent to the

Vught Vught () is a Municipalities of the Netherlands, municipality and a town in the southern Netherlands, and lies just south of the industrial and administrative centre of 's-Hertogenbosch. Many commuters live in the municipality, and the town of Vugh ...

concentration camp Internment is the imprisonment of people, commonly in large groups, without charges or intent to file charges. The term is especially used for the confinement "of enemy citizens in wartime or of terrorism suspects". Thus, while it can simply ...

for involvement with the Dutch Resistance. On September 5, 1944, the remaining prisoners of the camp (including the Roothaan brothers) were moved to the

Sachsenhausen Sachsenhausen () or Sachsenhausen-Oranienburg was a German Nazi concentration camp in Oranienburg, Germany, used from 1936 until April 1945, shortly before the defeat of Nazi Germany in May later that year. It mainly held political prisoners ...

camp in Germany ahead of the advancing Allies. Near the end of the war, the Sachsenhausen inmates were sent on a

death march A death march is a forced march of prisoners of war or other captives or deportees in which individuals are left to die along the way. It is distinguished in this way from simple prisoner transport via foot march. Article 19 of the Geneva Convent ...

which Roothaan's brother did not survive. While a prisoner of war he was able to pursue his studies in physics together with other professors and students under the formal guidance of

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...

. The work he was assigned to while cooperating with Philips was a foundation for his master's thesis. He obtained his master's degree in physics from

on October 14, 1945. After that he moved to USA, where he did his PhD thesis with

Robert S. Mulliken Robert Sanderson Mulliken Note Longuet-Higgins' amusing title for reference B238 1965 on page 354 of this Biographical Memoir. The title should be "Selected papers of Robert S Mulliken." (June 7, 1896 – October 31, 1986) was an American ph ...

from the

University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...

, on semiempirical MO theory, while holding a post at

The Catholic University of America The Catholic University of America (CUA) is a private university, private Catholic church, Roman Catholic research university in Washington, D.C. It is a pontifical university of the Catholic Church in the United States and the only institution ...

in Washington, D.C.. He realised that the then current approach to

molecular orbital theory In chemistry, molecular orbital theory (MO theory or MOT) is a method for describing the electronic structure of molecules using quantum mechanics. It was proposed early in the 20th century. In molecular orbital theory, electrons in a molecule ...

was incorrect and changed his topic to what resulted in the development of the

Roothaan equations The Roothaan equations are a representation of the Hartree–Fock equation in a non orthonormal basis set which can be of Gaussian-type or Slater-type. It applies to closed-shell molecules or atoms where all molecular orbitals or atomic orbitals ...

. Prof. Mulliken mentions this work in his Nobel lecture as follows: He had moved to the University of Chicago in 1949 and his PhD was awarded in 1950. He then joined the Physics Department of the University of Chicago. From 1962 to 1968 he was Director of the University of Chicago Computation Center. Later he was Professor of Physics and Chemistry at the University of Chicago. Since his retirement, in 1988, he has worked for the

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

Laboratories in

Palo Alto, California Palo Alto (; Spanish language, Spanish for "tall stick") is a charter city in the northwestern corner of Santa Clara County, California, United States, in the San Francisco Bay Area, named after a Sequoia sempervirens, coastal redwood tree kno ...

, where his primary contribution has been in the development of the mathematical coprocessor routines for the

Itanium Itanium ( ) is a discontinued family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Launched in June 2001, Intel marketed the processors for enterprise servers and high-performance computin ...

chip. His method of analyzing pipeline architecture has been unique and innovative and greatly admired in supercomputer circles around the world. In 1982 Roothaan became a correspondent of the

Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...

. He was a member of the

International Academy of Quantum Molecular Science The International Academy of Quantum Molecular Science (IAQMS) is an international scientific learned society covering all applications of quantum theory to chemistry and chemical physics. It was created in Menton in 1967. The founding members wer ...

and the Society of Catholic Scientists. He turned 100 in August 2018 and died in June 2019.

Works

Autobiographies

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References

External links

* {{DEFAULTSORT:Roothaan, Clemens 1918 births 2019 deaths Dutch centenarians Men centenarians 20th-century Dutch physicists Dutch emigrants to the United States Dutch Roman Catholics Catholic University of America faculty Members of the International Academy of Quantum Molecular Science University of Chicago alumni University of Chicago faculty Delft University of Technology alumni People from Nijmegen Theoretical chemists Members of the Royal Netherlands Academy of Arts and Sciences Computational chemists

Biography

Works

Autobiographies

See also

References

External links