Peter Debye

Peter Joseph William Debye ForMemRS[1] (/dɛˈbaɪ/;[2] Dutch: [dəˈbɛiə]; March 24, 1884 – November 2, 1966) was a Dutch-American physicist and physical chemist, and Nobel laureate in Chemistry.

Peter Debye
BornMarch 24, 1884
Maastricht, Netherlands
DiedNovember 2, 1966 (aged 82)
CitizenshipNetherlands / United States
Alma materRWTH Aachen
University of Munich
Known forDebye model
Debye relaxation
Debye frequency
AwardsRumford Medal (1930)
Faraday Lectureship Prize (1933)
Lorentz Medal (1935)
Nobel Prize in Chemistry (1936)
Willard Gibbs Award (1949)
Max Planck Medal (1950)
Priestley Medal (1963)
National Medal of Science (1965)
Scientific career
FieldsPhysics, Chemistry
InstitutionsUniversity of Zurich (1911–12)
University of Utrecht (1912–14)
University of Göttingen (1914–20)
ETH Zurich (1920–27)
University of Leipzig (1927–34)
University of Berlin (1934–39)
Cornell University (1940–50)
Doctoral advisorArnold Sommerfeld
Doctoral studentsLars Onsager
Paul Scherrer
George K. Fraenkel
Fritz Zwicky


Early life

Born Petrus Josephus Wilhelmus Debije[3] in Maastricht, Netherlands, Debye enrolled in the Aachen University of Technology in 1901. In 1905, he completed his first degree in electrical engineering. He published his first paper, a mathematically elegant solution of a problem involving eddy currents, in 1907. At Aachen, he studied under the theoretical physicist Arnold Sommerfeld, who later claimed that his most important discovery was Peter Debye.

In 1906, Sommerfeld received an appointment at Munich, Bavaria, and took Debye with him as his assistant. Debye got his Ph.D. with a dissertation on radiation pressure in 1908. In 1910, he derived the Planck radiation formula using a method which Max Planck agreed was simpler than his own.

In 1911, when Albert Einstein took an appointment as a professor at Prague, Bohemia, Debye took his old professorship at the University of Zurich, Switzerland. This was followed by moves to Utrecht in 1912,[4] to Göttingen in 1913, to ETH Zurich in 1920, to University of Leipzig in 1927, and in 1934 to Berlin, where, succeeding Einstein, he became director of the Kaiser Wilhelm Institute for Physics (now named the Max-Planck-Institut) whose facilities were built only during Debye's era. He was awarded the Lorentz Medal in 1935. From 1937 to 1939 he was the president of the Deutsche Physikalische Gesellschaft.

In May 1914 he became member of the Royal Netherlands Academy of Arts and Sciences and in December of the same year he became foreign member.[5]

Family and Personal Life

Debye was described as a martinet when it came to scientific principles, yet was always approachable and made time for his students. His personal philosophy emphasized a fulfillment of purpose and enjoyment in one's work. Debye was an avid trout fisherman and gardener, collector of cacti, and was "always known to enjoy a nice cigar".[6]

While in Berlin as an assistant to Arnold Sommerfeld, Debye became acquainted with Mathilde Alberer.[7] Mathidle was the daughter of the proprietor of the boarding house in which Debye was staying at.[7] Malthide would soon change her citizenship and in 1913, Debye married Mathilde Alberer.[7][8] Debye would enjoy working in his rose garden with Mathilde Albere late into his years.[6] They had a son, Peter P. Debye (1916-2012), and a daughter, Mathilde Maria (born 1921). Peter became a physicist and collaborated with Debye in some of his researches, and had a son who was also a chemist.[8]

Scientific contributions

His first major scientific contribution was the application of the concept of dipole moment to the charge distribution in asymmetric molecules in 1912, developing equations relating dipole moments to temperature and dielectric constant. In consequence, the units of molecular dipole moments are termed debyes in his honor. Also in 1912, he extended Albert Einstein's theory of specific heat to lower temperatures by including contributions from low-frequency phonons. See Debye model.

In 1913, he extended Niels Bohr's theory of atomic structure, introducing elliptical orbits, a concept also introduced by Arnold Sommerfeld. In 1914–1915, Debye calculated the effect of temperature on X-ray diffraction patterns of crystalline solids with Paul Scherrer (the "Debye–Waller factor"). In 1923, together with his assistant Erich Hückel, he developed an improvement of Svante Arrhenius' theory of electrical conductivity in electrolyte solutions. Although an improvement was made to the Debye–Hückel equation in 1926 by Lars Onsager, the theory is still regarded as a major forward step in our understanding of electrolytic solutions. Also in 1923, Debye developed a theory to explain the Compton effect, the shifting of the frequency of X-rays when they interact with electrons.

Later work

From 1934 to 1939 Debye was director of the physics section of the prestigious Kaiser Wilhelm Institute in Berlin. From 1936 onwards he was also professor of Theoretical Physics at the Frederick William University of Berlin. These positions were held during the years that Adolf Hitler ruled Nazi Germany and, from 1938 onward, Austria.

In 1939 Debye traveled to the United States to deliver the Baker Lectures at Cornell University in Ithaca, New York. After leaving Germany in early 1940, Debye became a professor at Cornell, chaired the chemistry department for 10 years, and became a member of Alpha Chi Sigma. In 1946 he became an American citizen. Unlike the European phase of his life, where he moved from city to city every few years, in the United States Debye remained at Cornell for the remainder of his career. He retired in 1952, but continued research until his death.

Much of Debye's work at Cornell concerned the use of light-scattering techniques (derived from his X-ray scattering work of years earlier) to determine the size and molecular weight of polymer molecules. This started as a result of his research during World War II on synthetic rubber, but was extended to proteins and other macromolecules.

In April 1966, Debye suffered a heart attack, and in November of that year a second one proved fatal. He is buried in the Pleasant Grove Cemetery (Ithaca, New York, USA).[9][10]

War activities and controversies

2006 controversy

In January 2006, a book (in Dutch) appeared in The Netherlands, written by Sybe Rispens, entitled Einstein in the Netherlands.[11] One chapter of this book discusses the relationship between Albert Einstein and Debye. Rispens discovered documents that, as he believed, were new and proved that, during his directorship of the Kaiser Wilhelm Society, Debye was actively involved in cleansing German science institutions of Jewish and other "non-Aryan elements". Rispens records that on December 9, 1938, Debye wrote in his capacity as chairman of the Deutsche Physikalische Gesellschaft (DPG) to all the members of the DPG:

In light of the current situation, membership by German Jews as stipulated by the Nuremberg laws, of the Deutsche Physikalische Gesellschaft cannot be continued. According to the wishes of the board, I ask of all members to whom these definitions apply to report to me their resignation. Heil Hitler!

Many biographies[1][12][13] published before Rispens' work, state that Debye moved to the US because he refused to accept German citizenship forced on to him by the Nazis. He planned his departure from Germany during a visit with his mother in Maastricht in late 1939, boarded a ship in Genoa in January 1940 and arrived in New York in early February 1940. He immediately sought a permanent position in the US and accepted such an offer from Cornell in June 1940. That month, he crossed the US border into Canada and returned within days on an immigration visa. He was able to get his wife out of Germany and to the US by December 1940. Although his son already was in the US before he departed, Peter Debye's 19-year-old daughter and his sister-in-law did not leave. They lived in his official residence in Berlin and were supported by Debye's official Berlin wages (he carefully maintained an official leave of absence for this purpose).

Further, Rispens[11] alleges that Albert Einstein in the first half of 1940 actively tried to prevent Debye from being appointed in the United States at Cornell. Einstein allegedly wrote to his American colleagues: "I know from a reliable source that Peter Debye is still in close contact with the German (Nazi) leaders" and, according to Rispens, called upon his colleagues to do "what they consider their duty as American citizens". To support this, Rispens refers to a well-known letter from Debye to Einstein and Einstein's response to it. Van Ginkel[14] investigated 1940 FBI reports on this matter and traced the "reliable source" to a single letter directed to Einstein and written by someone whose name is lost. This person was not known personally to Einstein and, according to Einstein, probably did not know Debye personally either. Moreover, this accusatory letter did not reach Einstein directly but was intercepted by British censors who showed it to Einstein. Einstein sent the British agent with the letter to Cornell, and the Cornell authorities told Debye about the affair. Thereupon Debye wrote his well-known 1940 letter to Einstein to which Einstein answered. The latter two letters can be found in the published Einstein correspondence.

Rispens alleges that Debye sent a telegram to Berlin on 23 June 1941 informing his previous employers that he was able and willing to resume his responsibilities at the Kaiser Wilhelm Institut, presumably in order to maintain his leave of absence and keep the Berlin house and wages available for his daughter. A copy of this telegram has not been recovered thus far. In summer 1941, Debye filed his intent to become a US citizen and was quickly recruited in the US to participate in the Allied War research.

It has been well documented in many biographies, and also in Rispens' book, that Debye and Dutch colleagues helped his Jewish colleague Lise Meitner in 1938–1939 (at great risk to himself and his family[15][16]) cross the Dutch-German border to escape Nazi persecution and eventually obtain a position in Sweden.

Predating Rispens' work, and in contrast to it, an article by Rechenberg[17] appeared 18 years earlier concerning Debye's letter. The article describes Debye's missive in more detail and presents a very favorable picture of Debye in his efforts to resist the Nazi activists. Moreover, this article points out that Max von Laue, well known for his anti-Nazi views, gave his approval to the letter from the DPG chairman.

International response

Debye's son, Peter P. Debye, interviewed in 2006 at age 89[18] recollects that his father was completely apolitical and that in the privacy of their home politics were never discussed. According to his son, Debye just wanted to do his job at the Kaiser Wilhelm Institute and as long as the Nazis did not bother him was able to do so. He recalls that his mother urged him (the son) to stay in the US in the event of war. Debye's son had come to the US on a planned 2-month vacation during the summer of 1939 and never returned to Germany because war did, indeed, break out.

In an opinion article published on the Debye Institute website, Dr. Gijs van Ginkel, until April 2007 Senior Managing Director of the VM Debye Instituut in Utrecht[19] deplored this decision. In his article he cites scholars who point out that the DPG was able to retain their threatened staff as long as could be expected under increasing pressure from the Nazis. He also puts forward the important argument that when Debye in 1950 received the Max Planck medal of the DPG, nobody objected, not even the known opponent of the national socialists Max von Laue, who would have been in a position to object. Also Einstein, with his enormous prestige, was still alive, as were other Jewish scientists such as Lise Meitner and James Franck who both knew Debye intimately. None of them protested against Debye's receiving the highest German scientific distinction. In fact, Albert Einstein, after many years of not participating in the voting for the Max Planck Medal nominees, joined the process again to vote for Debye.

Maastricht, University hospital, Monument for Peter Debye
Monument for Peter Debye in the Maastricht square that bears his name: Dipole moments (Felix van de Beek, 1998)

Maastricht University also announced that it was reconsidering its position on the Peter Debye Prijs voor natuurwetenschappelijk onderzoek (Peter Debye Prize for scientific research).[20]

In a reply on the DPG website,[21] Dieter Hoffmann and Mark Walker also conclude that Debye was not a Nazi activist. They remark that Max von Laue also was required and obliged (as a civil servant) to sign letters with Heil Hitler. They also state that the DPG was one of the last scientific societies to purge the Jewish members and only very reluctantly. They quote the response of the Reich University Teachers League (a National Socialist organization) to the Debye letter:

Obviously the German Physical Society is still very backward and still clings tightly to their dear Jews. It is in fact remarkable that only "because of circumstances beyond our control" the membership of Jews can no longer be maintained

In May 2006,[22] the Dutch Nobel Prize winner Martinus Veltman who had written the foreword to the Rispen book, renounced the book's description of Peter Debye, withdrew his foreword, and asked the Board of Directors of Utrecht University to rescind their decision to rename the Debye Institute.

Various historical investigations, both in The Netherlands and in the US, have been carried out subsequent to the actions of the University of Maastricht. The earliest of these investigations, carried out by the Cornell University's department of Chemistry and Chemical Biology is now complete. The report[23] of the Cornell investigation, released on 31 May 2006, states that:

Based on the information to-date, we have not found evidence supporting the accusations that Debye was a Nazi sympathizer or collaborator or that he held anti-Semitic views. It is important that this be stated clearly since these are the most serious allegations.

It goes on to declare:

Thus, based on the information, evidence and historical record known to date, we believe that any action that dissociates Debye's name from the Department of Chemistry and Chemical Biology at Cornell is unwarranted.

In June 2006, it was reported[24][25] that the scientific director of the (formerly) Debye Institute had been reprimanded by the Board of Directors of the University of Utrecht for a new publication on Debye's war years on the grounds that it was too personally biased with respect to the Institute's naming dispute. According to the board, the book should have been published not as a Debye Institute publication, but as a personal one. The book[14] was banned by the University of Utrecht and both Directors of the (former) Debye Institute were forbidden to have any further contact with the press. A dozen professors of the Physics Faculty, amongst whom Cees Andriesse, openly protested against the interventions of the Board and the censorship of their protest by the university.[26]

In May 2007, the universities of Utrecht and Maastricht announced that a new committee headed by Jan Terlouw would advise them regarding the name change. Also, in the beginning of 2007 an official report was announced, to be published by the NIOD and authorized by the Dutch Education Ministry (then scheduled for fall 2007).[27]

2007 NIOD report

The report describes Rispens' presentation of Debye, as an opportunist who had no objection to the Nazis, as a caricature.

[I]t can be stated that Debye was rightly called an opportunist after his arrival in the United States. We have seen that he showed himself to be loyal to the dominant political system, first in the Third Reich and then in the United States, while at the same time keeping the back door open: in the Third Reich by retaining his Dutch nationality, in the United States by attempting to secretly maintain some contacts with Nazi Germany via the Foreign Office.

It concludes that Debye's actions in 1933–45 were based on the nineteenth-century positivist view of science which saw research in physics as generating blessings for humankind. The report states that, by his contemporaries, Debye was considered an opportunist by some and as a man of highest character by others. The report asserts that Debye was not coerced by the Nazis into writing the infamous DPG Heil Hitler letter and that he also did not follow the lead of other societies in doing so but, rather, other societies followed his lead.[28] The NIOD report also concludes that Debye felt obliged to send the letter and that it was, for him, simply a confirmation of an existing situation. The report argues that Debye, in the Third Reich, developed a survival method of ambiguity which allowed him to pursue his scientific career despite the political turmoil. Crucial to this survival method was the need to keep ready an escape hatch, for example in his secret dealings with the Nazis in 1941, if needed.

Yet, the report also states that the picture of Debye should not be oversimplified as Debye's actions were also motivated by his loyalty to his daughter, who had remained in Berlin. In general, Debye developed a survival method of ambiguity, that "could pull the wool over people's eyes".[29]

2008 Terlouw report

In January 2008 the Terlouw Commission advised the Boards of Utrecht and Maastricht Universities to continue to use Peter Debye’s name for the chemistry and physics institute in Utrecht, and to continue awarding the science prize in Maastricht.[30] The Commission concluded that Debye was not a party member, was not an anti-semite, did not further Nazi propaganda, did not cooperate with the Nazi war machine, was not a collaborator, and yet also was not a resistance hero. He was a rather pragmatic, flexible, and brilliant scientist, idealistic with respect to the pursuit of science, but only superficially oriented in politics. With respect to sending out the DPG letter, the Commission concluded that Debye found the situation inescapable. The Commission pointed out that the Royal Dutch Academy of Sciences also took away Albert Einstein's honorary membership, emphasizing the circumstances in which these decisions had been taken. The Commission stated that now, seventy years later, no judgment can be made concerning the decision of Debye to sign this letter in the exceptionally difficult circumstances in which he then found himself. Nevertheless, the Commission describes the DPG letter as an extraordinarily unpleasant fact, forming a dark page in his life history. Finally, the Commission concluded that based on the NIOD report since no bad faith on Debye’s part has been demonstrated, his good faith must be assumed and recommended that the University of Utrecht retain the name of the Debye Institute of NanoMaterials Science and that the University of Maastricht continue to associate itself with the Peter Debye Prize. Utrecht University accepted the recommendation, Maastricht University did not. But in February 2008, the Hustinx Foundation (Maastricht), originator and sponsor of the Peter Debye Prize, announced that it will continue to have the prize awarded. The City of Maastricht, Debye's birthplace, declared that it sees no reason to change the names of Debye Street and Debye Square.

Debye the spy

In a 2010 publication Jurrie Reiding asserts that Debye may have been an MI6 spy.[31][32] Reiding discovered that Debye was befriended by the well-documented spy Paul Rosbaud. They first met around 1930 when they were both working as editors for two scientific journals. They collaborated in the escape of Lise Meitner in 1938. According to Reiding, Debye was well connected in German scientific and industrial circles and could have provided MI6 with valuable information. For example, as board member of the German Academy for Aviation Research he was acquainted with Hermann Göring. Reiding also offers an explanation for Debye's hasty departure on 16 January 1940 for the United States: the date coincided with the planned (but later delayed) German invasion of the Netherlands a day later, information possibly passed on to him by Rosbaud.

This hypothesis is contested by Philip Ball, as he notes that friendship with Rosbaud is no gauge of Debye's political stance. Rosbaud was well-connected with many people and Debye, while he was a friend of Rosbaud's, seems to have also felt regard for geologist Friedrich Drescher-Kaden, an ardent Nazi.[33]

Awards and honors



  1. ^ a b Davies, M. (1970). "Peter Joseph Wilhelm Debye. 1884–1966". Biographical Memoirs of Fellows of the Royal Society. 16: 175–232. doi:10.1098/rsbm.1970.0007.
  2. ^ Random House Dictionary, Random House, 2013: "Debye".
  3. ^ For Dutch use of "y" and "ij", see IJ (digraph)
  4. ^ Debye's predecessor in the chair of theoretical physics at Utrecht was Cornelis Wind, who died in 1911. Debye's successor at Utrecht was Leonard Ornstein.
  5. ^ "Peter Joseph Wilhelm Debije (1884 - 1966)". Royal Netherlands Academy of Arts and Sciences. Retrieved 27 July 2015.
  6. ^ a b Davies, Mansel (1970). "Peter Joseph Wilhelm Debye. 1884-1966". Biographical Memoirs of Fellows of the Royal Society. 16: 175–232. doi:10.1098/rsbm.1970.0007. JSTOR 769588.
  7. ^ a b c Laylin, James K. (1993-10-30). Nobel Laureates in Chemistry, 1901-1992. Chemical Heritage Foundation. ISBN 9780841226906.
  8. ^ a b Towson University Daily Digest Archived 2011-11-20 at the Wayback Machine. Retrieved on 2012-07-25.
  9. ^ "Peter Joseph Wilhelm Debye (1884–1966)". Retrieved 2009-03-27.
  10. ^ Debye is buried in the rear section of the cemetery, near the northwestern corner.
  11. ^ a b Sybe Rispens, Einstein in Nederland. Een intellectuele biografie Ambo/Anthos 2006 ISBN 90-263-1903-7
  12. ^ Stichting Edmond Hustinx and Christian Bremen (eds). Pie Debije-Peter Debye: 1884–1966. Gardez! Verlag (2000) ISBN 3897960486.
  13. ^ Williams, J. W. "Peter Joseph Wilhelm Debye" Biographical Memoirs, Vol. 46 (1975) National Academy of Sciences U.S.
  14. ^ a b G. van Ginkel, Prof. Peter J. W. Debye in 1935–1945. An investigation of historical sources, December 2006, ISBN 90-393-4284-9
  15. ^ Sime, Ruth Lewin. Lise Meitner: A Life in Physics. University of California Press (1997) ISBN 0520208609.
  16. ^ Sime, Ruth Lewin (1990). "Lise Meitner's Escape from Germany". American Journal of Physics. 58 (3): 262–267. Bibcode:1990AmJPh..58..262S. doi:10.1119/1.16196.
  17. ^ H. Rechenberg, Physik. Blätter, 44, Nov 1988, page 418
  18. ^ Interview given to Gooi & Eemlander newspaper (Dutch language) on 2 February 2006
  19. ^ Gijs van Ginkel (2006) AFSCHEID VAN DEBYE DOOR UTRECHT: EEN BESTUURLIJKE DWALING Archived 2007-02-25 at the Wayback Machine. (in Dutch)
  20. ^ Opgeroepen beeld moeilijk verenigbaar met voorbeeldfunctie UM, Press release University of Maastricht, 16 February 2006
  21. ^ Dieter Hoffmann and Mark Walker (March 2006). Peter Debye: A Typical Scientist in an Untypical Time Archived 2007-09-27 at the Wayback Machine.
  22. ^ "Veltman letter to the Utrecht University's Board of Directors". Archived from the original on December 23, 2007. Retrieved 2006-07-11.CS1 maint: BOT: original-url status unknown (link). 5 May 2006. Retrieved on 2012-07-25.
  23. ^ Héctor D. Abruña. "Decision Cornell University". Archived from the original on January 9, 2007. Retrieved 2006-07-11.CS1 maint: BOT: original-url status unknown (link). Retrieved on 2012-07-25.
  24. ^ Enserink M (2006). "ETHICS: Blocking a Book, Dutch University Rekindles Furor Over Nobelist Debye". Science. 312 (5782): 1858. doi:10.1126/science.312.5782.1858. PMID 16809496.
  25. ^ Arjan Dijkgraaf (20 June 2006) UU weer beschuldigd van censuur. Chemisch Weekblad (in Dutch).
  26. ^ Volkskrant, 24 March 2007.
  27. ^ NRC Handelsblad, 19 May 2007.
  28. ^ Note that this statement is in sharp contrast to the conclusion reached in a previous study of the DPG's relationship to the Third Reich which describes the DPG to be one of the last professional organizations in Germany to expel its Jewish members. Dieter Hoffmann (2001) Zwischen Autonomie und Anpassung: Die Deutsche Physikalische Gesellschaft im Dritten Reich. Max Planck Institute for the History of Science
  29. ^ Eickhoff, Martijn "In the Name of Science?", Aksant, Amsterdam, 2008, p. 131.
  30. ^ Terlouw Commission: ‘Continue using Debye’s name’. Press release University of Utrecht. 17 January 2008.
  31. ^ Ball, Philip (2010). "Letters defend Nobel laureate against Nazi charges". Nature. doi:10.1038/news.2010.656.
  32. ^ Reiding, Jurrie (2010). "Peter Debye: Nazi Collaborator or Secret Opponent?". Ambix. 57 (3): 275–300. doi:10.1179/174582310X12849808295706. PMID 21465996.
  33. ^ Philip Ball, Serving the Reich: The Struggle for the Soul of Physics under Hitler, 2014, ISBN 978-0-226-20457-4, page 141.
  34. ^ National Science Foundation – The President's National Medal of Science. (1966-02-10). Retrieved on 2012-07-25.
  35. ^ "Fraternity - Awards - Hall of Fame - Alpha Chi Sigma".

Further reading

External links


The debye (symbol: D) (; Dutch: [dəˈbɛiə]) is a CGS unit (a non-SI metric unit) of electric dipole moment named in honour of the physicist Peter J. W. Debye. It is defined as 1×10−18 statcoulomb-centimetre. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10−10 statcoulomb (generally called e.s.u. (electrostatic unit) in older literature), which were separated by 1 ångström. This gave a convenient unit for molecular dipole moments.

Typical dipole moments for simple diatomic molecules are in the range of 0 to 11 D. Symmetric homoatomic species, e.g. chlorine, Cl2, have zero dipole moment, and highly ionic molecular species have a very large dipole moment, e.g. gas-phase potassium bromide, KBr, with a dipole moment of 10.5 D.The debye is still used in atomic physics and chemistry because SI units are inconveniently large. The smallest SI unit of electric dipole moment is the yoctocoulomb-metre, which is roughly 300,000 D. There is currently no satisfactory solution to this problem of notation without resorting to the use of scientific notation.

Debye (crater)

Debye is a lunar impact crater that is located in the northern hemisphere on the Moon's far side, as seen from the Earth. It lies to the south of the crater Chappell, to the southwest of the walled plain Rowland, and to the east of D'Alembert.

The outer rim of this crater has been heavily battered by impacts, and is somewhat distorted from the form of a circle. The northeast rim in particular has become straightened by impact modification, and the crater rim as a whole has a roughly polygonal shape. The southern rim is overlaid by the smaller crater Perkin. The most heavily eroded section of the rim is along the northeast, where a cluster of overlapping craters intrudes into the side. The western rim is notched and indented by several small impacts.

The crater interior is nearly as battered as the outer rim. The outer rampart of Perkin intrudes part way across the southern floor. Parts of remaining interior have been bombarded and churned by impacts, leaving an irregular surface that is nearly as rough as the terrain that surrounds the crater. The most recent of these impacts is a small, cup-shaped crater just to the southwest of the midpoint.

Debye (disambiguation)

The debye (symbol: D) is a unit of electric dipole moment named after physicist Peter J. W. Debye

Debye may also refer to:

Peter Debye (1884–1966), Dutch physicist, physical chemist and Nobel laureate in Chemistry

30852 Debye, a main-belt asteroid named after Peter Debye

Debye (crater), a lunar crater named after Peter Debye

List of things named after Peter Debye

Debye frequency

The Debye frequency (Symbol: or ) is a parameter in the Debye model. It refers to a cut-off angular frequency for waves a harmonic chain of masses, used to describe the movement of ions in a crystal lattice and more specifically, to correctly predict the heat capacity in such crystals to be constant for high temperatures (Dulong-Petit law). The term was first introduced by Peter Debye in 1912.

Throughout this whole article periodic boundary conditions are assumed.

Debye function

In mathematics, the family of Debye functions is defined by

The functions are named in honor of Peter Debye, who came across this function (with n = 3) in 1912 when he analytically computed the heat capacity of what is now called the Debye model.

Debye length

In plasmas and electrolytes, the Debye length (also called Debye radius), named after Peter Debye, is a measure of a charge carrier's net electrostatic effect in a solution and how far its electrostatic effect persists. A Debye sphere is a volume whose radius is the Debye length. With each Debye length, charges are increasingly electrically screened. Every Debye‐length , the electric potential will decrease in magnitude by 1/e. Debye length is an important parameter in plasma physics, electrolytes, and colloids (DLVO theory). The corresponding Debye screening wave vector for particles of density , charge at a temperature is given by in Gaussian units. Expressions in MKS units will be given below. The analogous quantities at very low temperatures () are known as the Thomas-Fermi length and the Thomas-Fermi wave vector. They are of interest in describing the behaviour of electrons in metals at room temperature.

Debye sheath

The Debye sheath (also electrostatic sheath) is a layer in a plasma which has a greater density of positive ions, and hence an overall excess positive charge, that balances an opposite negative charge on the surface of a material with which it is in contact. The thickness of such a layer is several Debye lengths thick, a value whose size depends on various characteristics of plasma (e.g. temperature, density, etc.).

A Debye sheath arises in a plasma because the electrons usually have a temperature on the order of magnitude or greater than that of the ions and are much lighter. Consequently, they are faster than the ions by at least a factor of . At the interface to a material surface, therefore, the electrons will fly out of the plasma, charging the surface negative relative to the bulk plasma. Due to Debye shielding, the scale length of the transition region will be the Debye length . As the potential increases, more and more electrons are reflected by the sheath potential. An equilibrium is finally reached when the potential difference is a few times the electron temperature.

The Debye sheath is the transition from a plasma to a solid surface. Similar physics is involved between two plasma regions that have different characteristics; the transition between these regions is known as a double layer, and features one positive, and one negative layer.

Debye–Falkenhagen effect

The increase in the conductivity of an electrolyte solution when the applied voltage has a very high frequency is known as Debye–Falkenhagen effect. Impedance measurements on water-p-dioxane and the methanol-toluene systems have confirmed Falkenhagen's predictions made in 1929.

Debye–Hückel theory

The Debye–Hückel theory was proposed by Peter Debye and Erich Hückel as a theoretical explanation for departures from ideality in solutions of electrolytes and plasmas. It is a linearized Poisson–Boltzmann model, which assumes an extremely simplified model of electrolyte solution but nevertheless gave accurate predictions of mean activity coefficients for ions in dilute solution. The Debye–Hückel equation provides a starting point for modern treatments of non-ideality of electrolyte solutions.

Debye–Waller factor

The Debye–Waller factor (DWF), named after Peter Debye and Ivar Waller, is used in condensed matter physics to describe the attenuation of x-ray scattering or coherent neutron scattering caused by thermal motion. It has also been called the B factor or the temperature factor. Often, "Debye-Waller factor" is used as a generic term that comprises the Lamb-Mössbauer factor of incoherent neutron scattering and Mössbauer spectroscopy.

The DWF depends on the scattering vector q. For a given q, DWF(q) gives the fraction of elastic scattering; 1 - DWF(q) correspondingly gives the fraction of inelastic scattering. (Strictly speaking, this probability interpretation is not true in general.) In diffraction studies, only the elastic scattering is useful; in crystals, it gives rise to distinct Bragg reflection peaks. Inelastic scattering events are undesirable as they cause a diffuse background — unless the energies of scattered particles are analysed, in which case they carry valuable information (for instance in inelastic neutron scattering or electron energy loss spectroscopy).

The basic expression for the DWF is given by

where u is the displacement of a scattering center, and denotes either thermal or time averaging.

Assuming harmonicity of the scattering centers in the material under study, the Boltzmann distribution implies that is normally distributed with zero mean. Then, using for example the expression of the corresponding characteristic function, the DWF takes the form

Note that although the above reasoning is classical, the same holds in quantum mechanics.

Assuming also isotropy of the harmonic potential, one may write

where q, u are the magnitudes (or absolute values) of the vectors q, u respectively, and is the mean squared displacement. In crystallographic publications, values of are often given where . Note that if the incident wave has wavelength , and it is elastically scattered by an angle of , then

In the context of protein structures, the term B-factor is used. The B-factor is defined as

It is measured in units of Å2. The B-factors can be taken as indicating the relative vibrational motion of different parts of the structure. Atoms with low B-factors belong to a part of the structure that is well ordered. Atoms with large B-factors generally belong to part of the structure that is very flexible. Each ATOM record (PDB file format) of a crystal structure deposited with the Protein Data Bank contains a B-factor for that atom.

Ivar Waller

Ivar Waller (11 June 1898 – 12 April 1991) was a Swedish professor of theoretical physics at Uppsala University. He developed the theory of X-ray scattering by lattice vibrations of a crystal, building upon the prior work of Peter Debye. The Debye–Waller factor, which he introduced in his doctoral thesis in 1925, is the definitive treatment of the effect of thermal vibrations in X-ray crystallography. He was a member of the Royal Swedish Academy of Sciences from 1945, and the Nobel Committee for Physics 1945-1972.

One of his notable doctoral students was the quantum chemist Per-Olov Löwdin.

List of things named after Peter Debye

The article is a list of things named after the Dutchman P. J. W. Debye.

Debye – a unit of electric dipole moment

Debye–Hückel equation

Debye–Hückel limiting law, see Debye–Hückel equation

Debye–Hückel theory, see Debye–Hückel equation

Debye–Scherrer method, see Powder diffraction

Debye–Scherrer rings, see Debye–Scherrer method

Debye–Waller factor

Debye frequency, see also Debye model

Debye function, see also Debye model

Debye length

Debye model

Debye relaxation

Debye sheath

Debye shielding

Lorenz–Mie–Debye theory

Norman Davidson (biologist)

Norman Ralph Davidson (April 5, 1916 – February 14, 2002) was an American molecular biologist notable for advancing genome research, member of the National Academy of Sciences, received a National Medal of Science from U.S. President Bill Clinton, was a professor at Caltech. The New York Times called Davidson "major figure in advancing genome research ... whose groundbreaking work in molecular biology led to the earliest understanding of the overall structure of genomes".

The Los Angeles Times called him "a groundbreaking Caltech chemical biologist".

President Bill Clinton cited the scientist for "breakthroughs in chemistry and biology which have led to the earliest understanding of the overall structure of genomes".

Peter Debye Award

The Peter Debye Award in Physical Chemistry is awarded annually by the American Chemical Society "to encourage and reward outstanding research in physical chemistry". The award is named after Peter Debye and

granted without regard to age or nationality.

Physikalische Zeitschrift

Physikalische Zeitschrift (English: Physical Journal) was a German scientific journal of physics published from 1899 to 1945 by S. Hirzel Verlag. Several publications of great historical significance have been published in it, such as Albert Einstein's "Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung" (On the Development of Our Views Concerning the Nature and Constitution of Radiation) andCarl von Weizsäcker's work on the source of energy in stars. During its life, it was edited by several prominent physicists, such as Peter Debye.

Some of the early volumes (before 1908) are available on

RWTH Aachen Faculty of Electrical Engineering and Information Technology

The Faculty of Electrical Engineering and Information Technology is one of nine faculties at the RWTH Aachen University. It was separated from the Faculty of Mechanical Engineering in 1961. RWTH has produced several notable individuals. Nobel laureate Peter Debye received a degree in electrical engineering. Furthermore Bodo von Borries, Professor of Electrical Engineering was a co-inventor of electron microscope. Traditionally, the faculty is recognized for its strength in research. Several projects are assisted by the Deutsche Forschungsgemeinschaft and the European Union. Concerning funding by the German Research Foundation (Deutsche Forschungsgemeinschaft), from 2011 to 2013 in its field of activity the faculty obtained the highest funding nationwide.In 2014, more than 4,200 students were enrolled in the faculty.

RWTH Aachen Faculty of Mathematics, Computer science, and Natural sciences

The Faculty of Mathematics, Computer science, and Natural sciences is one of nine faculties at the RWTH Aachen University. It comprises five sections for mathematics, computer science, physics, chemistry and biology. The Faculty was founded in 1880 and produced several notable individuals like Arnold Sommerfeld and Nobel laureates Philipp Lenard, Wilhelm Wien, Johannes Stark or Karl Ziegler. Peter Debye studied Physics at the RWTH Aachen and won the Nobel Prize in 1936. Furthermore, Helmut Zahn and his team of the Institute for textile chemistry were the first who synthesised Insulin.

The faculty cooperates with Forschungszentrum Jülich and the 4 Fraunhofer Institutes in Aachen. Several projects are assisted by the Deutsche Forschungsgemeinschaft and the European Union. Approximately 6,100 students are enrolled in the faculty.

Rotational Brownian motion

Rotational Brownian motion is the random change in the orientation of a polar molecule due to collisions with other molecules. It is an important element of theories of dielectric materials.

The polarization of a dielectric material is a competition between torques due to the imposed electric field, which tend to align the molecules, and collisions, which tend to destroy the alignment. The theory of rotational Brownian motion allows one to calculate the net result of these two competing effects, and to predict how the permittivity of a dielectric material depends on the strength and frequency of the imposed electric field.

Rotational Brownian motion was first discussed by Peter Debye, who applied Einstein's theory of translational Brownian motion to the rotation of molecules having permanent electric dipoles. Debye ignored inertial effects and assumed that the molecules were spherical, with an intrinsic, fixed dipole moment. He derived expressions for the dielectric relaxation time and for the permittivity. These formulae have been successfully applied to many materials. However, Debye's expression for the permittivity predicts that the absorption tends toward a constant value when the frequency of the applied electric field becomes very large—the "Debye plateau". This is not observed; instead, the absorption tends toward a maximum and then declines with increasing frequency.

The breakdown in Debye's theory in these regimes can be corrected by including inertial effects; allowing the molecules to be non-spherical; including dipole-dipole interactions between molecules; etc. These are computationally very difficult problems and rotational Brownian motion is a topic of much current research interest.

Woldemar Voigt

Woldemar Voigt (German: [foːkt]; 2 September 1850 – 13 December 1919) was a German physicist, who taught at the Georg August University of Göttingen. Voigt eventually went on to head the Mathematical Physics Department at Göttingen and was succeeded in 1914 by Peter Debye, who took charge of the theoretical department of the Physical Institute. In 1921, Debye was succeeded by Max Born.

Nobel Prize laureates from The Netherlands
Nobel Peace Prize
Nobel Prize in Physics
Nobel Prize in Chemistry
Nobel Memorial Prize in Economic Sciences
Nobel Prize in Physiology or Medicine
Scientists whose names are used as units
SI base units
SI derived units
Non-SI metric (cgs) units
Imperial and US customary units
Non-systematic units

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