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[[category:Scientists]][[category:Physicists]] [[category: Professor at the ULB-VUB]] [[category:Mathematicians]] [[category: Thermodynamics]] [[category:Chemists]] [[category: Birth 1851-1875]][[category: Professors]] [[category:members Academy]]
[[File:De donder.png|270px|right|thumb|Source: Glansdorff, Paul, Bosquet, Jean en Géhéniau, Jules, [http://www.academieroyale.be/academie/documents/DEDONDERTheophileARB_19878521.pdf "Notice sur Théophile De Donder"], in: ''Annuaire Académie Royale de Belgique'', (1987)]]
Physicist and chemist considered a founder of the thermodynamics of irreversible processes. Born on 19 August 1872 in Schaerbeek and died on 11 May 1957 in Brussels.

===Biography===
De Donder was working as a teacher of mathematics at the lyceum of Sint-Gillis when he obtained his doctorate in mathematics and physics at the [[University of Brussels]] in 1899.<ref>One of his students at the lyceum was [[Defay, Raymond (1897-1988)|Raymond Defay]]. Grégoire Nicolis, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0040.php "De thermodynamica, de wetenschap van het niet-lineaire en de statische mechanica" ], in: {{Halleux 2}}, 167.</ref> 
After completing his doctorate, De Donder served an internship with Henri Poincaré. In 1911, he was appointed by the [[University of Brussels]] as lecturer of the mathematical physics course at the Faculty of Sciences and Applied Sciences. After World War I, he was promoted to the chair of mathematical physics. De Donder taught courses on thermodynamics and physical chemistry there.
<ref>Pierre Marage, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0035.php "De kernfysica en de deeltjesfyscia"], in: {{Halleux 2}}, 89. </ref> 
Through the efforts of his pupil [[Van den Dungen, Frans (1898-1965)|Frans Van den Dungen]], these courses became one of the starting points of the [[Brussels school of thermodynamics]] which was later made famous by [[Prigogine, Ilya (1917-2003)|Ilya Prigogine]].
<ref> Marage, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0035.php "De kernfysica en de deeltjesfyscia"], 85.</ref> 
[[Nuyens, Karel Maurice (1901-1970)|Maurice Nuyens]], [[Van Hove, Léon (1924-1990)|Léon Van Hove]], [[Van Mieghem, Jacques (1905-1980)|Jacques Van Mieghem]], [[Lemaître, Georges Henri Joseph Édouard (1894-1966)|Georges Lemaître]] were pupils of De Donder. A Belgian school of relativity was thus established.

De Donder was admitted to emeritus status in 1942.

The mathematician was appointed corresponding member of [[The Royal Academies for Science and the Arts of Belgium|Académie royale des Sciences et Belles-Lettres de Bruxelles]] in 1919 and member in 1929. In 1937, he was elected director of the Class of Sciences,
<ref> Glansdorff, "Théophile De Donder", 54.</ref> 
De Donder co-founded and was the first president of the [[Belgian Mathematical Society]]. From 1924, he also actively participated in the [[Solvay conferences]]. Furthermore, De Donder served on the administrative council of the [[National Fund for Scientific Research (FNRS-NFWO)]] and on the international jury of the [[Francqui Prize]]. He was chairman of the Science Council of the [[Royal Observatory of Belgium]]. He was laureate of the Belgian Government's [[Ten-Yearly Prize of the Belgian Government for Applied Mathematical Sciences|Ten-Yearly Prize for Applied Mathematical Sciences for the period 1913-1922]].
<ref> Glansdorff, "Théophile De Donder", 354.</ref> 
An interesting fact is that in addition to being a scientist, De Donder was also a gifted musician and composed several pieces for piano.

In 1958, a year after his death, the [[Théophile De Donder Prize]] was established in his honour.


===Works===
De Donder was a prolific author: he wrote more than two hundred articles and communications and a dozen books. He also maintained an extensive correspondence with renowned professional colleagues such as Louis de Broglie, Arthur Eddington, Hendrik Antoon Lorentz, Vito Volterra and Albert Einstein.
<ref> Jean Mawhin,  [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0034.php "De wiskunde"], in: {{Halleux 1}}, 107.</ref> 
De Donders doctorate entitled ''"Sur la Théorie des Invariants Intégraux"'', dealt with integral invariants. After a stay in Paris, where he worked with Henri Poincaré, he further devoted himself to the theory of integral invariants, the calculus of variations and the theory of relativity.
<ref> Pierre,  [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0035.php "De kernfysica en de deeltjesfyscia"], 131. </ref>

=====Mathematical publications=====
At the [[ULB]], De Donder's ideas and enthusiasm were at the heart of a flourishing mathematical tradition. Thanks to [[Lepage, Théophile Henri Joseph (1901-1991)|Théophile Lepage]], a student of De Donder, the external differential calculus gained new applications.
<ref> Mawhin, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0034.php "De wiskunde"], 71.</ref> 
Influenced by his teacher Poincaré, De Donder developed the theory of integral invariants and pioneered, what would later would be called, the theory of external differential forms. The latter was indispensable in mathematics and theoretical physics. De Donder used the works of Elvin Christopher (1829-1900), Gregorio Ricci (1853-192) and Tullio Levi-Civita (1873-1941) on absolute differential calculus as early as 1904.
<ref> Mawhin, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0034.php "De wiskunde"], 106.</ref> 
He was also inspired by [[De Tilly, Joseph Marie (1837-1906)|Joseph Marie De Tilly's]] work on non-euclidean mechanics.
<ref> Mawhin,[http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0034.php "De wiskunde"], 111.</ref>

=====Relativity theory=====
A convinced relativist, De Donder had been following Albert Einstein's research with close interest since 1914. In 1916, when Einstein's ''Grundlage der allgemeinen Relativitätstheorie'' was published, the Belgian mathematician was one of the first scientists to correspond with the German scholar about his theory of gravitation and general relativity. As one of the few physicists who understood the theory of relativity at this time, De Donder was the key player in the reception of Einstein's theories in Belgium. Not only did he manage to transfer his enthusiasm for Einstein's theory to his students, in particular to [[Géhéniau, Jules (1909-1991)|Jules Géhéniau]], but in his own work too, De Donder developed and disseminated Einstein's ideas and in some places put them on point. In 1922, for example, he published the important work ''La gravifique einsteinienne''. In it, he tried to translate general relativity into the calculus of variations. In doing so, his mathematical point of view sometimes differed completely from Einstein's physical point of view. The influence of De Donder's courses and work was decisive for the history of general relativity and of cosmology in Belgium.
<ref> Marage, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0035.php "De kernfysica en de deeltjesfyscia"], 81.</ref> 

From 1920 onwards, together with [[Vanderlinden, Henri Louis (1892-1983)|Henri Vanderlinden]], De Donder studied solutions to Einstein's equations corresponding to a spherically symmetric (but not necessarily homogeneous) space, and the equations of the gravitational field in the presence of a source of an electromagnetic field.
<ref>Dominque Lambert,[http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0038.php "De algemene relativiteit en de kosmologie"], in: {{Halleux 2}}, 131. </ref>

=====Thermodynamics=====
In thermodynamics, De Donder introduced a new formulation of the second law, based on the concept of "affinity". Despite his preference for fundamental physical theories and abstract mathematical formulations, he quickly recognised the potential of applying chemical thermodynamics, based on the concept of affinity, to systems with non-equilibrium states. He developed a correlation between chemical affinity and Gibbs free energy. This led to the development and expansion of the thermodynamics of irreversible processes: where irreversibility had used to remain confined to the framework of thermodynamics, De Donder showed there was also a kinetical dimension to irreversibility. To put it differently: De Donder opened the door to kinetics. <br>
With the development of this theory, De Donders became the founder of the Brussels school of thermodynamics of non-reversible processes and mathematical physics. He and his school were the only ones engaged in truly creative theorisation during this period.
<ref> Nicolis, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0040.php "De thermodynamica, de wetenschap van het niet-lineaire en de statische mechanica"],156. </ref> 
It was his pupil [[Prigogine, Ilya (1917-2003)|Ilya Prigogine]], who would further extend and complete De Donder's theory. He completed his PhD under De Donder's guidance. Under the impetus of [[Defay, Raymond (1897-1988)|Raymond Defay]], a systematic extension of thermodynamics was developed with the addition of surface effects.
<ref> Nicolis, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0040.php "De thermodynamica, de wetenschap van het niet-lineaire en de statische mechanica"], 167.</ref> 
De Donder's school had a decisive influence on the young [[Lemaître, Georges Henri Joseph Édouard (1894-1966) |Georges Lemaître]]. 

=====Surface science=====
The physicochemistry of low-dimensional systems (electrodes, membranes, catalytic surfaces, micro-emulsions, films) has attracted the attention of Belgian researchers. One of the first works in this direction, dedicated to galvinistic batteries, was by De Donder in collaboration with his pupil [[Van Lerberghe, Georges (1896 - 1940)|Georges van Lerberghe]].<ref>Nicolis, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0040.php "De thermodynamica, de wetenschap van het niet-lineaire en de statische mechanica"], 167. </ref>



===Publications===
Van De Donders hand zijn onder meer bekend:
*''Sur la théorie des invariants intégraux'', Thesis, 1899.
* ''Théorie du champ électromagnétique de Maxwell-Lorentz et du champ gravifique d'Einstein'', Parijs, 1917.
* ''La gravifique Einsteinienne'', 1921.
*''Introduction à la gravifique einsteinienne'', 1925.
*''Théorie des champs gravifiques'', Parijs, 1926.
*''The Mathematical Theory of Relativity'', Cambridge, 1927.
*''Application de la gravifique einsteinienne'', Parijs, 1930.
*''Application de la gravifique einsteinienne à l'électrodynamique des corps en mouvement'', Parijs, 1932.
*''Théorie invariantive du calcul des variations'', Parijs, 1935.
*''Thermodynamic Theory of Affinity: A Book of Principles'', Oxford, 1936. 
*''The Mathematical Theory of Relativity'', Cambridge, 1937. 

<br/>

===Bibliography===
*  Marage, Pierre, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0035.php "De kernfysica en de deeltjesfyscia"], in: {{Halleux 2}}
*  Lambert, Dominque,[http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0038.php "De algemene relativiteit en de kosmologie"], in: {{Halleux 2}}
* Nicolis, Grégoire, [http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0040.php "De thermodynamica, de wetenschap van het niet-lineaire en de statische mechanica"], in: {{Halleux 2}}.
* Glansdorff, Paul, ,"Théophile De Donder", in:''Ciel et Terre'', 73, 354-356. 
* Mawhin, Jean,[http://www.dbnl.org/tekst/hall014gesc02_01/hall014gesc02_01_0034.php "De wiskunde"], in: {{Halleux 1}}.
*[http://www.academieroyale.be/academie/documents/FichierPDFBiographieNationaleTome2095.pdf#page=123 De Donder, Théophile], in: ''Biographie Nationale'', 37(1971), 240-245.
* Glansdorff, Paul, Bosquet, Jean en Géhéniau, Jules, [http://www.academieroyale.be/academie/documents/DEDONDERTheophileARB_19878521.pdf "Notice sur Théophile De Donder"], in: ''Annuaire Académie Royale de Belgique'', (1987).
*Van den Dungen, Frans, "Théophile De Donder", in: ''Revue de l'universiteé de Bruxelles'', 10 (1958), nr. 4-5, 293-302.
*Géhéniau, Jules, "Théophile De Donder 1872-1957", in: ''Florilège des Sciences'', 1968, 169-182.


* The [https://catalogue.archives.ulb.be/downloads/archives-de-theophile-de-donder.pdf ULB archives] store many publications and notes by and on Théophile De Donder.
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===Notes===
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