Clemens C. J. Roothaan
Encyclopedia
Clemens C.J. Roothaan was born in 1918 in Nijmegen, the Netherlands
. He enrolled TU Delft in 1935 to study electrical engineering
. During World War II
he was first detained as a prisoner of war camp, later he was sent for a year to a concentration camp in Vught
. 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
. The work he was assigned to while cooperating with Philips was a foundation for his master's thesis. He obtained his masters degree in physics from TU Delft on October 14, 1945. After that he moved to USA, where he did his PhD thesis with Robert S. Mulliken
from the University of Chicago
, on semiempirical MO theory, while holding a post at The Catholic University of America
in Washington, D.C.
. He realised that the then current approach to molecular orbital theory
was incorrect and changed his topic to what resulted in the development of the Roothaan equations
. 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 Centre. 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
Laboratories in Palo Alto, California
, where his primary contribution has been in the development of the mathematical coprocessor routines for the Itanium chip. His method of analyzing pipeline architecture has been unique and innovative and greatly admired in supercomputer circles around the world.
He is a member of the International Academy of Quantum Molecular Science
.
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
. He enrolled TU Delft in 1935 to study electrical engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
. During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
he was first detained as a prisoner of war camp, later he was sent for a year to a concentration camp in Vught
Vught
Vught is a municipality and a town in the southern Netherlands. It is a town where lots of commuters live and has recently been named "Best place to live" by the Dutch magazine Elsevier.-Politics:...
. 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
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
. The work he was assigned to while cooperating with Philips was a foundation for his master's thesis. He obtained his masters degree in physics from TU Delft on October 14, 1945. After that he moved to USA, where he did his PhD thesis with Robert S. Mulliken
Robert S. Mulliken
Robert Sanderson Mulliken was an American physicist and chemist, primarily responsible for the early development of molecular orbital theory, i.e. the elaboration of the molecular orbital method of computing the structure of molecules. Dr. Mulliken received the Nobel Prize for chemistry in 1966...
from the University of Chicago
University of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...
, on semiempirical MO theory, while holding a post at The Catholic University of America
The Catholic University of America
The Catholic University of America is a private university located in Washington, D.C. in the United States. It is a pontifical university of the Catholic Church in the United States and the only institution of higher education founded by the U.S. Catholic bishops...
in Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
. He realised that the then current approach to molecular orbital theory
Molecular orbital theory
In chemistry, molecular orbital theory is a method for determining molecular structure in which electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule...
was incorrect and changed his topic to what resulted in the development of the Roothaan equations
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, respectively, are doubly occupied. This is generally...
. 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 Centre. 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
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
Laboratories in Palo Alto, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, where his primary contribution has been in the development of the mathematical coprocessor routines for the Itanium chip. His method of analyzing pipeline architecture has been unique and innovative and greatly admired in supercomputer circles around the world.
He is a member of the International Academy of Quantum Molecular Science
International Academy of Quantum Molecular Science
The International Academy of Quantum Molecular Science 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 were Raymond Daudel, Per-Olov Löwdin, Robert G. Parr, John...
.