The van der Waals equation is an equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion and R^-6 van der Waals attraction). The van der Waals equation is an Equation of state for a Fluid composed of particles that have a non-zero size and a pairwise attractive inter-particle Force In Physics and Thermodynamics, an equation of state is a relation between state variables More specifically an equation of state is a thermodynamic

In physical chemistry, the name van der Waals force refers to the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral molecules. Physical chemistry, is the application of Physics to macroscopic microscopic atomic subatomic and particulate phenomena in chemical systems It is mostly defined as a large In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge ^[1] The term includes:

• dipole–dipole forces
• hydrogen bonding
• London (instantaneous dipole-induced dipole) forces

It is also sometimes used loosely as a synonym for the totality of intermolecular forces. Van der Waals forces are relatively weak compared to normal chemical bonds, but play a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. Supramolecular chemistry refers to the area of Chemistry that focuses on the Noncovalent bonding interactions of molecules Structural biology is the branch of Molecular biology concerned with the Architecture and shape of biological Macromolecules especially Proteins Polymer science or macromolecular science is the subfield of Materials science concerned with Polymers primarily synthetic polymers such as Plastics Nanotechnology, sometimes shortened to nanotech, refers to a field of Applied science whose theme is the control of matter on an Atomic and Molecular Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including Solid - Liquid Condensed matter physics is the field of Physics that deals with the macroscopic physical properties of Matter. It is named after the Dutch scientist Johannes Diderik van der Waals. Johannes Diderik van der Waals ( November 23, 1837 &ndash March 8, 1923) was a Dutch Scientist and Thermodynamicist Van der Waals forces define the chemical character of many organic compounds. They also define the solubility of organic substances in polar and unpolar mediums. In low alcohols, the properties of the polar hydroxyl group dominate the weak intermolecular forces of Van der Waals. In higher alcohols, the properties of the unpolar alkyl rest (R) dominate and define the solubility. Van der Waals forces grow with the length of the non polar part of the substance.

Definition

Van der Waals forces include momentary attractions between molecules, diatomic free elements, and individual atoms. Diatomic molecules are molecules made only of two Atoms of either the same or different Chemical elements The prefix di- means two in Greek They differ from covalent and ionic bonding in that they are not stable, but are caused by momentary polarization of particles. An ionic bond (or electrovalent bond) is a type of Chemical bond that can often form between Metal and Non-metal Ions (or Because electrons have no fixed position in the structure of an atom or molecule, but rather are distributed in a probabilistic fashion based on quantum probability, there is a non-negligible chance that the electrons are not evenly distributed and thus their electrical charges are not evenly distributed. See Schrödinger equation for the theories on wave functions and descriptions of position and velocity of quantum particles. In Physics, especially Quantum mechanics, the Schrödinger equation is an equation that describes how the Quantum state of a Physical system

To explain this, we refer to the article on intermolecular forces, where it is discussed that an intermolecular force has four major contributions. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of In general an intermolecular potential has a repulsive part, prohibiting the collapse of molecular complexes, and an attractive part. The attractive part, in turn, consists of three distinct contributions:

1. The electrostatic interactions between charges (in the case of molecular ions), dipoles (in the case of molecules without inversion center), quadrupoles (all molecules with symmetry lower than cubic), and in general between permanent multipoles. The electrostatic interaction is sometimes called Keesom interaction or Keesom force after Willem Hendrik Keesom. Willem Hendrik Keesom ( June 21, 1876, Texel &ndash March 24 1956, Leiden) was a Dutch Physicist
2. The second source of attraction is induction (also known as polarization), which is the interaction between a permanent multipole on one molecule with an induced multipole on another. This interaction is sometimes measured in debyes after Peter J.W. Debye. The debye (symbol D) is a non- SI, CGS unit of electrical dipole moment. Peter Joseph William Debye ( March 24 1884 &ndash November 2 1966) was a Dutch physicist and physical chemist
3. The third attraction is usually named after Fritz London who himself called it dispersion. Fritz Wolfgang London ( March 7, 1900 &ndash March 30, 1954) was a German -born American theoretical Physicist. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of This is the only attraction experienced by noble gas atoms, but it is operative between any pair of molecules, irrespective of their symmetry. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity

Returning to nomenclature: some texts mean by the van der Waals force the totality of forces (including repulsion), others mean all the attractive forces (and then sometimes distinguish van der Waals-Keesom, van der Waals-Debye, and van der Waals-London), and, finally some use the term "van der Waals force" solely as a synonym for the London/dispersion force. So, if you come across the term "van der Waals force", it is important to ascertain to which school of thought the author belongs.

All intermolecular/van der Waals forces are anisotropic (except those between two noble gas atoms), which means that they depend on the relative orientation of the molecules. Anisotropy (pronounced with stress on the third syllable ˌænaɪˈsɒtrəpi is the property of being directionally dependent as opposed to Isotropy, which means homogeneity The induction and dispersion interactions are always attractive, irrespective of orientation, but the electrostatic interaction changes sign upon rotation of the molecules. That is, the electrostatic force can be attractive or repulsive, depending on the mutual orientation of the molecules. When molecules are in thermal motion, as they are in the gas and liquid phase, the electrostatic force is averaged out to a large extent, because the molecules thermally rotate and thus probe both repulsive and attractive parts of the electrostatic force. Sometimes this effect is expressed by the statement that "random thermal motion around room temperature can usually overcome or disrupt them" (which refers to the electrostatic component of the van der Waals force). Clearly, the thermal averaging effect is much less pronounced for the attractive induction and dispersion forces.

The Lennard-Jones potential is often used as an approximate model for the isotropic part of a total (repulsion plus attraction) van der Waals force as a function of distance. A pair of neutral atoms or molecules is subject to two distinct forces in the limit of large separation and small separation an attractive force at long ranges ( van der Waals force, or

Van der Waals forces are responsible for certain cases of pressure broadening (van der Waals broadening) of spectral lines and the formation of van der Waals molecules. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared A van der Waals molecule is a stable cluster consisting of two or more Molecules held together by Van der Waals forces or by Hydrogen bonds.

See this URL for an introductory description of the van der Waals force (as a sum of attractive components only).

London dispersion force

Interaction energy of argon dimer. This article pertains to the chemical element For other uses see Argon (disambiguation. A dimer is a Chemical or Biological entity consisting of two subunits called Monomers which are held together by either Intramolecular forces The long-range part is due to London dispersion forces

London dispersion forces, named after the German-American physicist Fritz London, are weak intermolecular forces that arise from the attractive force between transient dipoles (or better multipoles) in molecules without permanent multipole moments. A name ( Etymology: from OE nama akin to OHG namo, Latin Nomen, and Greek όνομα ( Fritz Wolfgang London ( March 7, 1900 &ndash March 30, 1954) was a German -born American theoretical Physicist. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Multipole moments are the Coefficients of a Series expansion of a Potential due to continuous or discrete sources (e London dispersion forces are also known as dispersion forces, London forces, or induced dipole-dipole forces.

London forces can be exhibited by nonpolar molecules because electron density moves about a molecule probabilistically (see quantum mechanical theory of dispersion forces). In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of There is a high chance that the electron density will not be evenly distributed throughout a nonpolar molecule. When an uneven distribution occurs, a temporary multipole is created. This multipole may interact with other nearby multipoles. London forces are also present in polar molecules, but they are usually only a small part of the total interaction force. The present is the Time that is perceived directly not as a recollection or a speculation In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by SMALL, Small Machine Algol Like Language is a programming language developed by Dr

Electron density in a molecule may be redistributed by proximity to another multipole. Electron density is the measure of the Probability of an Electron being present at a specific location Electrons will gather on the side of a molecule that faces a positive charge and will retreat from a negative charge. Hence, a transient multipole can be produced by a nearby polar molecule, or even by a transient multipole in another nonpolar molecule.

In vacuum, London forces are weaker than other intermolecular forces such as ionic interactions, hydrogen bonding, or permanent dipole-dipole interactions. In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen

This phenomenon is the only attractive intermolecular force at large distances present between neutral atoms (e. g. , helium), and is the major attractive force between non-polar molecules, (e. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical g. , nitrogen or methane). Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Without London forces, there would be no attractive force between noble gas atoms, and they could not then be obtained in a liquid form. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity

London forces become stronger as the atom (or molecule) in question becomes larger. This is due to the increased polarizability of molecules with larger, more dispersed electron clouds. This trend is exemplified by the halogens (from smallest to largest: F₂, Cl₂, Br₂, I₂). Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions Fluorine and chlorine are gases at room temperature, bromine is a liquid, and iodine is a solid. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and This page is about the physical properties of gas as a state of matter Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic The London forces also become stronger with larger amounts of surface contact. Greater surface area means closer interaction between different molecules. Surface area is the measure of how much exposed Area an object has

Relation to the Casimir effect

The London-van der Waals forces is related to the Casimir effect for dielectric media, the former the microscopic description of the latter bulk property. In Physics, the Casimir effect and the Casimir-Polder force are physical forces arising from a quantized field. The first detailed calculations of this were done in 1955 by E. M. Lifshitz. Evgeny Mikhailovich Lifshitz (Евгений Михайлович Лифшиц February 21 1915 &ndash October 29 1985) was a leading Soviet ^[2]

For further investigation, one may consult the University of St. Andrews' levitation work in a popular article: Science Journal: New way to levitate objects discovered, and in a more scholarly version: New Journal of Physics: Quantum levitation by left-handed metamaterials, which relate the Casimir effect to the gecko and how the reversal of the Casimir effect can result in physical levitation of tiny objects.

Use by animals

Gecko climbing glass using its natural setæ

The ability of geckos to climb on sheer surfaces has been attributed to van der Waals force^[3]. Geckos are small to average sized Lizards belonging to the family Gekkonidae which are found in warm climates throughout the world Seta (plural setae) is a biological term derived from the Latin word for " Bristle " Geckos are small to average sized Lizards belonging to the family Gekkonidae which are found in warm climates throughout the world A recent study suggests that water molecules of roughly monolayer thickness (present on all surfaces) also play a role. ^[4]. Nevertheless, a gecko can hang on a glass surface using only one toe. Efforts continue to create a synthetic "gecko tape" that exploits this knowledge. So far, research has produced some promising results - early research yielded an adhesive tape^[5] product, which only obtains a fraction of the forces measured from the natural material, and new research^[6] are being developed with the goal of featuring 200 times the adhesive forces of the natural material. Adhesive tape can be one of many varieties of backing materials coated with an Adhesive. Researchers at Rensselaer Polytechnic Institute and the University of Akron announced in a paper published in the June 18–22, 2007 issue of the Proceedings of the National Academy of Sciences that they have created a synthetic “gecko tape” with four times the sticking power of a natural gecko foot^[7].

Researchers at Stanford University and Carnegie Mellon University recently developed a gecko-like robot which uses synthetic setae to climb walls^[8]. Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private Research university located in Carnegie Mellon University (also known as CMU) is a private Research University in Pittsburgh, Pennsylvania, United A robot is a mechanical or Virtual Artificial agent In practice it is usually an electro-mechanical system which by its appearance or movements Synthetic setae emulate the Setae found on the toes of a Gecko and scientific research in this area is driven towards the development of Dry adhesives Geckos

Sources

• Iver Brevik, V. N. Marachevsky, Kimball A. Milton, Identity of the van der Waals Force and the Casimir Effect and the Irrelevance of these Phenomena to Sonoluminescence, hep-th/9901011
• I. D. Dzyaloshinskii, E. M. Lifshitz, and L. P. Pitaevskii, Usp. Fiz. Nauk 73, 381 (1961)
  • English translation: Soviet Phys. Usp. 4, 153 (1961)
• L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media, Pergamon, Oxford, 1960, pp. 368–376.
• Mark Lefers, "Van der Waals dispersion force". Holmgren Lab.
• E. M. Lifshitz, Zh. Eksp. Teor. Fiz. 29, 894 (1955)
  • English translation: Soviet Phys. JETP 2, 73 (1956)
• Western Oregon University's "London force". Intermolecular Forces. (animation)
• J. Lyklema, Fundamentals of Interface and Colloid Science, page 4. 43