Johannes Diderik van der Waals

Johannes Diderik van der Waals (Dutch pronunciation: [joːˈɦɑnəz ˈdidərɪk fɑn dɛr ˈʋaːls] (listen);[1] 23 November 1837 – 8 March 1923) was a Dutch theoretical physicist and thermodynamicist famous for his work on an equation of state for gases and liquids.

His name is primarily associated with the van der Waals equation of state that describes the behavior of gases and their condensation to the liquid phase. His name is also associated with van der Waals forces (forces between stable molecules),[2] with van der Waals molecules (small molecular clusters bound by van der Waals forces), and with van der Waals radii (sizes of molecules). As James Clerk Maxwell said about Van der Waals, "there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science."[3]

In his 1873 thesis, van der Waals noted the non-ideality of real gases and attributed it to the existence of intermolecular interactions. He introduced the first equation of state derived by the assumption of a finite volume occupied by the constituent molecules.[4] Spearheaded by Ernst Mach and Wilhelm Ostwald, a strong philosophical current that denied the existence of molecules arose towards the end of the 19th century. The molecular existence was considered unproven and the molecular hypothesis unnecessary. At the time van der Waals' thesis was written (1873), the molecular structure of fluids had not been accepted by most physicists, and liquid and vapor were often considered as chemically distinct. But van der Waals's work affirmed the reality of molecules and allowed an assessment of their size and attractive strength. His new formula revolutionized the study of equations of state. By comparing his equation of state with experimental data, Van der Waals was able to obtain estimates for the actual size of molecules and the strength of their mutual attraction.[5] The effect of Van der Waals's work on molecular physics in the 20th century was direct and fundamental.[6] By introducing parameters characterizing molecular size and attraction in constructing his equation of state, Van der Waals set the tone for modern molecular science. That molecular aspects such as size, shape, attraction, and multipolar interactions should form the basis for mathematical formulations of the thermodynamic and transport properties of fluids is presently considered an axiom.[7] With the help of the van der Waals's equation of state, the critical-point parameters of gases could be accurately predicted from thermodynamic measurements made at much higher temperatures. Nitrogen, oxygen, hydrogen, and helium subsequently succumbed to liquefaction. Heike Kamerlingh Onnes was significantly influenced by the pioneer work of van der Waals. In 1908, Onnes became the first to make liquid helium; this led directly to his 1911 discovery of superconductivity.[8]

Van der Waals started his career as a school teacher. He became the first physics professor of the University of Amsterdam when in 1877 the old Athenaeum was upgraded to Municipal University. Van der Waals won the 1910 Nobel Prize in physics for his work on the equation of state for gases and liquids.[9]

Johannes van der Waals
Johannes Diderik van der Waals
Born23 November 1837
Leiden, Netherlands
Died8 March 1923 (aged 85)
Amsterdam, Netherlands
NationalityDutch
Alma materUniversity of Leiden
Known forLaying the foundations for modern molecular physics (molecular theory)
Originating modern theory of intermolecular forces
Law of corresponding states
Real gas law
van der Waals forces
van der Waals equation of state
van der Waals radius
van der Waals surface
van der Waals molecule
AwardsNobel Prize for Physics (1910)
Scientific career
FieldsTheoretical physics, thermodynamics
InstitutionsUniversity of Amsterdam
Doctoral advisorPieter Rijke
Doctoral studentsDiederik Korteweg
Willem Hendrik Keesom
InfluencesRudolf Clausius
Ludwig Boltzmann
Josiah Willard Gibbs
Thomas Andrews
InfluencedHeike Kamerlingh Onnes
Willem Hendrik Keesom
Peter Debye
Zygmunt Florenty Wróblewski
James Dewar
Fritz London
Modern molecular science (including molecular physics and molecular dynamics)
Cryogenics

Biography

Early years and education

Johannes Diderik van der Waals was born on 23 November 1837 in Leiden in the Netherlands. He was the eldest of ten children born to Jacobus van der Waals and Elisabeth van den Berg. His father was a carpenter in Leiden. As was usual for working-class children in the 19th century, he did not go to the kind of secondary school that would have given him the right to enter university. Instead he went to a school of “advanced primary education”, which he finished at the age of fifteen. He then became a teacher's apprentice in an elementary school. Between 1856 and 1861 he followed courses and gained the necessary qualifications to become a primary school teacher and head teacher.

In 1862, he began to attend lectures in mathematics, physics and astronomy at the University in his city of birth, although he was not qualified to be enrolled as a regular student in part because of his lack of education in classical languages. However, the University of Leiden had a provision that enabled outside students to take up to four courses a year. In 1863 the Dutch government started a new kind of secondary school (HBS, a school aiming at the children of the higher middle classes). Van der Waals—at that time head of an elementary school—wanted to become a HBS teacher in mathematics and physics and spent two years studying in his spare time for the required examinations.

In 1865, he was appointed as a physics teacher at the HBS in Deventer and in 1866, he received such a position in The Hague, which was close enough to Leiden to allow van der Waals to resume his courses at the University there. In September 1865, just before moving to Deventer, van der Waals married the eighteen-year-old Anna Magdalena Smit.

Professorship

Van der Waals still lacked the knowledge of the classical languages that would have given him the right to enter university as a regular student and to take examinations. However, it so happened that the law regulating the university entrance was changed and dispensation from the study of classical languages could be given by the minister of education. Van der Waals was given this dispensation and passed the qualification exams in physics and mathematics for doctoral studies.

At Leiden University, on June 14, 1873, he defended his doctoral thesis Over de Continuïteit van den Gas- en Vloeistoftoestand (on the continuity of the gaseous and liquid state) under Pieter Rijke. In the thesis, he introduced the concepts of molecular volume and molecular attraction.[10]

In September 1877 van der Waals was appointed the first professor of physics at the newly founded Municipal University of Amsterdam. Two of his notable colleagues were the physical chemist Jacobus Henricus van 't Hoff and the biologist Hugo de Vries. Until his retirement at the age of 70 van der Waals remained at the Amsterdam University. He was succeeded by his son Johannes Diderik van der Waals, Jr., who also was a theoretical physicist. In 1910, at the age of 72, van der Waals was awarded the Nobel Prize in physics. He died at the age of 85 on March 8, 1923.

Scientific work

The main interest of van der Waals was in the field of thermodynamics. He was influenced by Rudolf Clausius' 1857 treatise entitled Über die Art der Bewegung, welche wir Wärme nennen (On the Kind of Motion which we Call Heat).[11][12] Van der Waals was later greatly influenced by the writings of James Clerk Maxwell, Ludwig Boltzmann, and Willard Gibbs. Clausius' work led him to look for an explanation of Thomas Andrews' experiments that had revealed, in 1869, the existence of critical temperatures in fluids.[13] He managed to give a semi-quantitative description of the phenomena of condensation and critical temperatures in his 1873 thesis, entitled Over de Continuïteit van den Gas- en Vloeistoftoestand (On the continuity of the gas and liquid state).[14] This dissertation represented a hallmark in physics and was immediately recognized as such, e.g. by James Clerk Maxwell who reviewed it in Nature[15] in a laudatory manner.

In this thesis he derived the equation of state bearing his name. This work gave a model in which the liquid and the gas phase of a substance merge into each other in a continuous manner. It shows that the two phases are of the same nature. In deriving his equation of state van der Waals assumed not only the existence of molecules (the existence of atoms was disputed at the time[16]), but also that they are of finite size and attract each other. Since he was one of the first to postulate an intermolecular force, however rudimentary, such a force is now sometimes called a van der Waals force.

A second great discovery was published in 1880, when he formulated the Law of Corresponding States. This showed that the van der Waals equation of state can be expressed as a simple function of the critical pressure, critical volume, and critical temperature. This general form is applicable to all substances (see van der Waals equation.) The compound-specific constants a and b in the original equation are replaced by universal (compound-independent) quantities. It was this law which served as a guide during experiments which ultimately led to the liquefaction of hydrogen by James Dewar in 1898 and of helium by Heike Kamerlingh Onnes in 1908.

In 1890, van der Waals published a treatise on the Theory of Binary Solutions in the Archives Néerlandaises. By relating his equation of state with the Second Law of Thermodynamics, in the form first proposed by Willard Gibbs, he was able to arrive at a graphical representation of his mathematical formulations in the form of a surface which he called Ψ (Psi) surface following Gibbs, who used the Greek letter Ψ for the free energy of a system with different phases in equilibrium.

Mention should also be made of van der Waals' theory of capillarity which in its basic form first appeared in 1893.[17] In contrast to the mechanical perspective on the subject provided earlier by Pierre-Simon Laplace,[18] van der Waals took a thermodynamic approach. This was controversial at the time, since the existence of molecules and their permanent, rapid motion were not universally accepted before Jean Baptiste Perrin's experimental verification of Albert Einstein's theoretical explanation of Brownian motion.

Personal life

He married Anna Magdalena Smit in 1865, and the couple had three daughters (Anne Madeleine, Jacqueline E. van der Waals, Johanna Diderica) and one son, the physicist Johannes Diderik van der Waals, Jr. Jacqueline was a poet of some note. Van der Waals' nephew Peter van der Waals was a cabinet maker and a leading figure in the Sapperton, Gloucestershire school of the Arts and Crafts movement. The wife of Johannes van der Waals died of tuberculosis at 34 years old in 1881. After becoming a widower Van der Waals never remarried and was so shaken by the death of his wife that he did not publish anything for about a decade. He died in Amsterdam on March 8, 1923, one year after his daughter Jacqueline had died.

His grandson, Christopher D. Vanderwal is a distinguished professor of Chemistry at the University of California, Irvine.

Honors

Van der Waals received numerous honors and distinctions, besides winning the 1910 Nobel Prize in Physics. He was awarded an honorary doctorate of the University of Cambridge; was made honorary member of the Imperial Society of Naturalists of Moscow, the Royal Irish Academy and the American Philosophical Society; corresponding member of the Institut de France and the Royal Academy of Sciences of Berlin; associate member of the Royal Academy of Sciences of Belgium; and foreign member of the Chemical Society of London, the National Academy of Sciences of the U.S., and of the Accademia dei Lincei of Rome. Van der Waals was a member of the Koninklijke Nederlandse Akademie van Wetenschappen (Royal Netherlands Academy of Sciences) since 1875.[19] From 1896 until 1912, he was secretary of this society.

Related quotes

...There can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science,
— James Clerk Maxwell's remarks in Nature magazine (1873).[3]
...It will be perfectly clear that in all my studies I was quite convinced of the real existence of molecules, that I never regarded them as a figment of my imagination, nor even as mere centres of force effects. I considered them to be the actual bodies, thus what we term "body" in daily speech ought better to be called "pseudo body". It is an aggregate of bodies and empty space. We do not know the nature of a molecule consisting of a single chemical atom. It would be premature to seek to answer this question but to admit this ignorance in no way impairs the belief in its real existence. When I began my studies I had the feeling that I was almost alone in holding that view. And when, as occurred already in my 1873 treatise, I determined their number in one gram-mol, their size and the nature of their action, I was strengthened in my opinion, yet still there often arose within me the question whether in the final analysis a molecule is a figment of the imagination and the entire molecular theory too. And now I do not think it any exaggeration to state that the real existence of molecules is universally assumed by physicists. Many of those who opposed it most have ultimately been won over, and my theory may have been a contributory factor. And precisely this, I feel, is a step forward. Anyone acquainted with the writings of Boltzmann and Willard Gibbs will admit that physicists carrying great authority believe that the complex phenomena of the heat theory can only be interpreted in this way. It is a great pleasure for me that an increasing number of younger physicists find the inspiration for their work in studies and contemplations of the molecular theory...
— Johannes D. van der Waals's notes in Nobel Lecture, The equation of state for gases and liquids (12 December 1910).

See also

References

This article incorporates material from the Citizendium article "Johannes Diderik van der Waals", which is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License but not under the GFDL.
  1. ^ Every word in isolation: [joːˈɦɑnəs ˈdidərɪk vɑn dɛr ˈʋaːls].
  2. ^ Parsegian, V. Adrian (2005). Van der Waals Forces: A Handbook for Biologists, Chemists, Engineers, and Physicists. (Cambridge University Press), p. 2. “The first clear evidence of forces between what were soon to be called molecules came from Johannes Diderik van der Waals' 1873 Ph.D. thesis formulation of the pressure p, volume V, and temperature T of dense gases.”
  3. ^ a b Johannes Diderik van der Waals - Biographical - Nobelprize.org
  4. ^ van der Waals; J. D. (1873). Over de continuiteit van den gas- en vloeistoftoestand (On the Continuity of the Gaseous and Liquid States) (doctoral dissertation). Universiteit Leiden.
  5. ^ Sengers, Johanna Levelt (2002), p. 16
  6. ^ Kipnis, A. Ya.; Yavelov, B. E.; Rowlinson, J. S.: Van der Waals and Molecular Science. (Oxford: Clarendon Press, 1996)
  7. ^ Sengers, Johanna Levelt (2002), p. 255-256
  8. ^ Blundell, Stephen: Superconductivity: A Very Short Introduction. (Oxford University Press, 1st edition, 2009, p. 20)
  9. ^ "The Nobel Prize in Physics 1910". Nobel Foundation. Retrieved October 9, 2008.
  10. ^ see the article on the van der Waals equation for the technical background
  11. ^ J.D. van der Waals, 1910, "The equation of state for gases and liquids," Nobel Lectures in Physics, pp. 254-265 (December 12, 1910), see [1], accessed 25 June 2015.
  12. ^ Clausius, R. (1857). "Über die Art der Bewegung, welche wir Wärme nennen". Annalen der Physik. 176 (3): 353–380. Bibcode:1857AnP...176..353C. doi:10.1002/andp.18571760302.
  13. ^ Andrews, T. (1869). "The Bakerian Lecture: On the Gaseous State of Matter". Philosophical Transactions of the Royal Society of London. 159: 575–590. doi:10.1098/rstl.1869.0021.
  14. ^ van der Waals, JD (1873) Over de Continuiteit van den Gas- en Vloeistoftoestand (on the continuity of the gas and liquid state). PhD thesis, Leiden, The Netherlands.
  15. ^ Maxwell, J.C. (1874). "Van der Waals on the Continuity of Gaseous and Liquid States". Nature. 10 (259): 477–480. Bibcode:1874Natur..10..477C. doi:10.1038/010477a0.
  16. ^ Tang, K.-T.; Toennies, J. P. (2010). "Johannes Diderik van der Waals: A Pioneer in the Molecular Sciences and Nobel Prize Winner in 1910". Angewandte Chemie International Edition. 49: 9574–9579. doi:10.1002/anie.201002332. PMID 21077069.
  17. ^ van der Waals, J.D. (1893). "Thermodynamische theorie der capillariteit in de onderstelling van continue dichtheidsverandering". Verhand. Kon. Akad. V Wetensch. Amst. Sect. 1 (Dutch; English translation in J. Stat. Phys., 1979, 20:197).
  18. ^ Laplace, P.S. (1806). Sur l'action capillaire (Suppl. au livre X, Traité de Mécanique Céleste). Crapelet; Courcier; Bachelier, Paris.
  19. ^ "Johannes Diderik van der Waals Senior (1837 - 1923)". Royal Netherlands Academy of Arts and Sciences. Retrieved July 17, 2015.

Further reading

  • Kipnis, A. Ya.; Yavelov, B. E.; Rowlinson, J. S.: Van der Waals and Molecular Science. (Oxford: Clarendon Press, 1996, 313pp) ISBN 0-19-855210-6
  • Sengers, Johanna Levelt: How Fluids Unmix: Discoveries by the School of Van der Waals and Kamerlingh Onnes (Edita - History of Science and Scholarship in the Netherlands). (Edita-the Publishing House of the Royal, 2002, 318pp)
  • Shachtman, Tom: Absolute Zero and the Conquest of Cold. (Boston: Houghton Mifflin, 1999)
  • Van Delft, Dirk: Freezing Physics: Heike Kamerlingh Onnes and the Quest for Cold. (Edita-the Publishing House of the Royal, 2008, 592pp)
  • Van der Waals, J. D.: Edited and Intro. J. S. Rowlinson: On the Continuity of the Liquid and Gaseous States. (New York: Dover Publications, 2004, 320pp)

External links

1837 in science

The year 1837 in science and technology involved some significant events, listed below.

1873 in science

The year 1873 in science and technology involved some significant events, listed below.

1880 in science

The year 1880 in science and technology included many events, some of which are listed here.

1923 in science

The year 1923 in science and technology involved some significant events, listed below.

Guillaume Daniel Delprat

Guillaume Daniel Delprat CBE (1 September 1856 – 15 March 1937) was a Dutch-Australian metallurgist, mining engineer, and businessman. He was a developer of the froth flotation process for separating minerals.Delprat was born in Delft, the Netherlands, son of Major General Felix Albert Theodore Delprat (1812–1888), later minister of war, and his wife Elisabeth Francina, née van Santen Kolff.

Delprat attended a high school in Amsterdam and later became an apprentice engineer on the Tay Bridge in Scotland. He attended science classes in Newport-on-Tay and learned calculus from his father by post. On returning to the Netherlands, he is said to have acted as assistant to Johannes Diderik van der Waals, physics professor at the University of Amsterdam. From 1879 to 1882, Delprat worked in Spain at the Tharsis Sulphur and Copper Mines.In 1898, chairman E. N. Wigg of Broken Hill Proprietary invited Delprat to Australia to become Assistant General Manager of BHP. He moved there with his wife and children. On 1 April 1899, he was promoted to General Manager, a position he held until 1921. At BHP, he pioneered the froth flotation process for refining sulphide ore. Delprat foresaw the exhaustion of BHP's mine at Broken Hill, and pushed for moving the company's smelters to Port Pirie; also construction of the Iron Knob railways. He shifted BHP from silver and lead mining to zinc and sulphur production. These moves were the basis of BHP's later success.Delprat also pushed construction of the BHP steelworks at Newcastle, New South Wales. The contract was signed on 24 September 1912 and the steelworks were opened by Governor-General Novar on 2 June 1915. For Delprat's visionary judgement in the project he was made a CBE.In 1935 Delprat was the first recipient of the medal of the Australasian Institute of Mining and Metallurgy.

Intermolecular force

Intermolecular forces (IMF) are the forces which mediate interaction between molecules, including forces of attraction or repulsion which act between molecules and other types of neighboring particles, e.g., atoms or ions. Intermolecular forces are weak relative to intramolecular forces – the forces which hold a molecule together. For example, the covalent bond, involving sharing electron pairs between atoms, is much stronger than the forces present between neighboring molecules. Both sets of forces are essential parts of force fields frequently used in molecular mechanics.

The investigation of intermolecular forces starts from macroscopic observations which indicate the existence and action of forces at a molecular level. These observations include non-ideal-gas thermodynamic behavior reflected by virial coefficients, vapor pressure, viscosity, superficial tension, and absorption data.

The first reference to the nature of microscopic forces is found in Alexis Clairaut's work Theorie de la Figure de la Terre. Other scientists who have contributed to the investigation of microscopic forces include: Laplace, Gauss, Maxwell and Boltzmann.

Attractive intermolecular forces are categorized into the following types:

Hydrogen bonding

Ionic bonding

Ion–induced dipole forces

Ion–dipole forces

van der Waals forces – Keesom force, Debye force, and London dispersion forceInformation on intermolecular forces is obtained by macroscopic measurements of properties like viscosity, pressure, volume, temperature (PVT) data. The link to microscopic aspects is given by virial coefficients and Lennard-Jones potentials.

John Shipley Rowlinson

Sir John Shipley Rowlinson (12 May 1926 – 15 August 2018) was a British chemist. He attended Oxford University where he completed his undergraduate studies in 1948 and doctoral in 1950. He then became research associate at University of Wisconsin (1950–1951), lecturer at University of Manchester (1951–1961), Professor at Imperial College London (1961–1973) and back at Oxford from 1974 to his retirement in 1993.

His works covered a wide range of subjects, including on capillarity (the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity) and cohesion (forces that make similar molecules stick together). In addition, he wrote about the history of science, including multiple works on the Dutch physicist Johannes Diderik van der Waals (1837–1923). He was a Fellow of the Royal Society and the Royal Academy of Engineering. He received a Faraday Lectureship Prize in 1983 and was knighted in 2000.

Peter Waals

Peter Waals (30 January 1870 – May 1937), born Pieter van der Waals, was a Dutch cabinet maker associated with the Arts and Crafts movement.

Theorem of corresponding states

According to van der Waals, the theorem of corresponding states (or principle/law of corresponding states) indicates that all fluids, when compared at the same reduced temperature and reduced pressure, have approximately the same compressibility factor and all deviate from ideal gas behavior to about the same degree.Material constants that vary for each type of material are eliminated, in a recast reduced form of a constitutive equation. The reduced variables are defined in terms of critical variables.

It originated with the work of Johannes Diderik van der Waals in about 1873 when he used the critical temperature and critical pressure to characterize a fluid.

The most prominent example is the van der Waals equation of state, the reduced form of which applies to all fluids.

VDW

VDW can refer to one of the following:

Van der Waals:

Johannes Diderik van der Waals, a Dutch physicist and thermodynamicist

the van der Waals force

the van der Waals equation

the van der Waals radius

Van der Waals (crater)

Federation of German Scientists (VDW)

Verbond tot Democratisering der Weermacht, a Dutch political party

VDW (TV station), a digital television station in Western Australia

HCSRN Virtual Data Warehouse, a data standard of the Health Care Systems Research Network, a health care research consortium

Van der Waals (crater)

Van der Waals is a lunar impact crater on the far side of the Moon. It is a heavily eroded feature with an irregular outer rim. The edge is lowest along the southern side where it is little more than a circular crest along the ground. It is more developed along the northern side, but the rim is notched and rugged. The satellite crater Van der Waals W is attached to the exterior of the northeast, and Van der Waals H intrudes into the rim along the southeast. The interior floor is relatively even and featureless, with only a few tiny craterlets to mark the surface.

Nearby craters of note include Clark to the north, Carver to the east, and Pikel'ner to the southeast. About two crater diameters to the west-southwest is Lebedev.

Van der Waals constants (data page)

The following table lists the van der Waals constants (from the van der Waals equation) for a number of common gases and volatile liquids.

To convert from to , multiply by 100.

Van der Waals equation

The van der Waals equation (or van der Waals equation of state; named after Johannes Diderik van der Waals) is an equation of state that generalizes the ideal gas law based on plausible reasons that real gases do not act ideally. The ideal gas law treats gas molecules as point particles that interact with their containers but not each other, meaning they neither take up space nor change kinetic energy during collisions. The ideal gas law states that volume (V) occupied by n moles of any gas has a pressure (P) at temperature (T) in kelvins given by the following relationship, where R is the gas constant:

PV = nRT,

To account for the volume that a real gas molecule takes up, the van der Waals equation replaces V in the ideal gas law with , where b is the volume that is occupied by one mole of the molecules. This leads to:

The second modification made to the ideal gas law accounts for the fact that gas molecules do in fact attract each other and that real gases are therefore more compressible than ideal gases. Van der Waals provided for intermolecular attraction by adding to the observed pressure P in the equation of state a term , where a is a constant whose value depends on the gas. The van der Waals equation is therefore written as:

and can also be written as the equation below

where Vm is the molar volume of the gas, R is the universal gas constant, T is temperature, P is pressure, and V is volume. When the molar volume Vm is large, b becomes negligible in comparison with Vm, a/Vm2 becomes negligible with respect to P, and the van der Waals equation reduces to the ideal gas law, PVm=RT.

It is available via its traditional derivation (a mechanical equation of state), or via a derivation based in statistical thermodynamics, the latter of which provides the partition function of the system and allows thermodynamic functions to be specified. It successfully approximates the behavior of real fluids above their critical temperatures and is qualitatively reasonable for their liquid and low-pressure gaseous states at low temperatures. However, near the transitions between gas and liquid, in the range of p, V, and T where the liquid phase and the gas phase are in equilibrium, the van der Waals equation fails to accurately model observed experimental behaviour, in particular that p is a constant function of V at given temperatures. As such, the van der Waals model is not useful only for calculations intended to predict real behavior in regions near the critical point. Empirical corrections to address these predictive deficiencies have been inserted into the van der Waals model, e.g., by James Clerk Maxwell in his equal area rule, and related but distinct theoretical models, e.g., based on the principle of corresponding states, have been developed to achieve better fits to real fluid behaviour in equations of more comparable complexity.

Van der Waals force

In molecular physics, the van der Waals force, named after Dutch scientist Johannes Diderik van der Waals, is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The Van der Waals force quickly vanishes at longer distances between interacting molecules.

Van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media.

If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der Waals contact distance; this phenomenon results from the mutual repulsion between the atoms' electron clouds. The van der Waals force has the same origin as the Casimir effect, arising from quantum interactions with the zero-point field.The term van der Waals force is sometimes used loosely for all intermolecular forces. The term always includes the London dispersion force between instantaneously induced dipoles. It is sometimes applied to the Debye force between a permanent dipole and a corresponding induced dipole or to the Keesom force between permanent molecular dipoles.

Van der Waals molecule

A van der Waals molecule is a weakly bound complex of atoms or molecules held together by intermolecular attractions such as van der Waals forces or by hydrogen bonds. The name originated in the beginning of the 1970s when stable molecular clusters were regularly observed in molecular beam microwave spectroscopy.

Van der Waals radius

The van der Waals radius, rw, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom. It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms were not simply points and to demonstrate the physical consequences of their size through the van der Waals equation of state.

Van der Waals strain

In chemistry, van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. Van der Waals strain is also called van der Waals repulsion and is related to steric hindrance. One of the most common forms of this strain is eclipsing hydrogen, in alkanes.

Van der Waals surface

The van der Waals surface of a molecule is an abstract representation or model of that molecule, illustrating where, in very rough terms, a surface might reside for the molecule based on the hard cutoffs of van der Waals radii for individual atoms, and it represents a surface through which the molecule might be conceived as interacting with other molecules. Also referred to as a van der Waals envelope, the van der Waals surface is named for Johannes Diderik van der Waals, a Dutch theoretical physicist and thermodynamicist who developed theory to provide a liquid-gas equation of state that accounted for the non-zero volume of atoms and molecules, and on their exhibiting an attractive force when they interacted (theoretical constructions that also bear his name). van der Waals surfaces are therefore a tool used in the abstract representations of molecules, whether accessed, as they were originally, via hand calculation, or via physical wood/plastic models, or now digitally, via computational chemistry software. Practically speaking, CPK models, developed by and named for Robert Corey, Linus Pauling, and Walter Koltun, were the first widely used physical molecular models based on van der Waals radii, and allowed broad pedagogical and research use of a model showing the van der Waals surfaces of molecules.

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