Per-Olov Löwdin (October 28, 1916 – October 6, 2000) was a Swedish
physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe.
Physicists generally are interested in the root or ultimate cau ...
, professor at the
University of Uppsala
Uppsala University ( sv, Uppsala universitet) is a public research university in Uppsala, Sweden. Founded in 1477, it is the oldest university in Sweden and the Nordic countries still in operation.
The university rose to significance during ...
from 1960 to 1983, and in parallel at the
University of Florida
The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...
until 1993.
A former graduate student under
Ivar Waller, Löwdin formulated in 1950 the symmetric
orthogonalization scheme for
atomic and
molecular orbital
In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of findin ...
calculations, greatly simplifying the
tight-binding method. This scheme is the basis of the
zero-differential overlap (ZDO) approximation used in semiempirical theories. In 1956 he introduced the canonical orthogonalization scheme, which is optimal for eliminating approximate linear dependencies of a basis set. These orthogonalization procedures are widely used today in all modern quantum chemistry calculations.
He is also credited with the use of fat symbols for
matrices
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** ''The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...
, making easy the derivation of several theorems of
quantum mechanics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistr ...
.
The famous 'Löwdin's pairing theorem' used in
restricted open-shell Hartree–Fock Restricted open-shell Hartree–Fock (ROHF) is a variant of Hartree–Fock method for open shell molecules. It uses doubly occupied molecular orbitals as far as possible and then singly occupied orbitals for the unpaired electrons. This is the sim ...
(ROHF),
unrestricted Hartree–Fock Unrestricted Hartree–Fock (UHF) theory is the most common molecular orbital method for open shell molecules where the number of electrons of each spin are not equal. While restricted Hartree–Fock theory uses a single molecular orbital ...
(UHF) and
generalized valence bond
The generalized valence bond (GVB) is a method in valence bond theory that uses flexible orbitals in the general way used by modern valence bond theory. The method was developed by the group of William A. Goddard, III around 1970.
Theory
The gene ...
(RES-GVB) theories is not his. According to himself,
George G. Hall and King made the formal proposition after an informal suggestion by Löwdin.
His Löwdin partitioning technique for
quantum chemistry problems is best appreciated through the series of 14 papers on
perturbation theory
In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middl ...
published between 1963 and 1971.
He was also a very active teacher, starting the ''Summer Schools of Quantum Chemistry'' at Uppsala around 1958. In 1959 and 1960, Löwdin started the Quantum Theory Project at the University of Florida as a sister project to the Uppsala Quantum Chemistry Group. In 1964 he was joined by
John C. Slater from MIT. The International Winter Institutes (held initially at Sanibel Island, and later at Gainesville) provided the initiation of hundreds of Latin American young scientists during the eighties and nineties. In 1960 he founded the
Sanibel Symposium The Sanibel Symposium is an international scientific conference in quantum chemistry, solid-state physics, and quantum biology. It has been organized by the Quantum Theory Project at the University of Florida in Gainesville, Florida, United Stat ...
in conjunction with the Winter Institute. They have been held every year since 1960.
Löwdin was elected a member of the
Royal Swedish Academy of Sciences in 1969, the
American Philosophical Society
The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
in 1983,
and was a member of the committee for the
Nobel Prize in Physics
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
from 1972 to 1984. He was the founder of the ''
International Journal of Quantum Chemistry
The ''International Journal of Quantum Chemistry'' is a peer-reviewed scientific journal publishing original, primary research and review articles on all aspects of quantum chemistry, including an expanded scope focusing on aspects of materials ...
'' and of the series ''
Advances in Quantum Chemistry''. He was a foundation 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 we ...
.
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References
External links
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* Kimio Ohn
Early Ideas in the history of Quantum Chemistry(1976)
Quantum Theory Projectfounded by Löwdin at the University of Florida in 1960
{{DEFAULTSORT:Lowdin, Per-Olov
Swedish physicists
1916 births
2000 deaths
University of Florida faculty
Academic staff of Uppsala University
Members of the International Academy of Quantum Molecular Science
Theoretical chemists
Members of the Royal Swedish Academy of Sciences
Fellows of the American Physical Society
Members of the American Philosophical Society