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 (UU) () 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.
Initially founded in the 15th century, the university rose to s ...
from 1960 to 1983, and in parallel at the
University of Florida
The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...
until 1993.
A former graduate student under
Ivar Waller, Löwdin formulated in 1950 the symmetric
orthogonalization
In linear algebra, orthogonalization is the process of finding a set of orthogonal vectors that span a particular subspace. Formally, starting with a linearly independent set of vectors in an inner product space (most commonly the Euclidean s ...
scheme for
atomic and
molecular orbital 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.
The famous 'Löwdin's pairing theorem' used in
restricted open-shell Hartree–Fock (ROHF),
unrestricted Hartree–Fock (UHF) and
generalized valence bond (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
Quantum chemistry, also called molecular quantum mechanics, is a branch of physical chemistry focused on the application of quantum mechanics to chemical systems, particularly towards the quantum-mechanical calculation of electronic contributions ...
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 middle ...
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 into quantum chemistry for hundreds of young Latin American scientists during the 1980s and 1990s. In 1960 he founded the
Sanibel Symposium in conjunction with the Winter Institute, held every year since then.
Löwdin was elected a member of the
Royal Swedish Academy of Sciences
The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ...
in 1969, the
American Philosophical Society
The American Philosophical Society (APS) is an American scholarly organization and learned society founded in 1743 in Philadelphia that promotes knowledge in the humanities and natural sciences through research, professional meetings, publicat ...
in 1983,
and was a member of the committee for the
Nobel Prize in Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
from 1972 to 1984. He was the founder of the ''
International Journal of Quantum Chemistry'' and of the series ''
Advances in Quantum Chemistry''. He was a foundation member of the
International Academy of Quantum Molecular Science.
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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