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In molecular physics and chemistry, the van der Waals force (sometimes van der Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds , these attractions do not result from a chemical electronic bond ; [ 2 ] they are comparatively weak and therefore more susceptible to disturbance.
London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, fluctuating induced dipole bonds [1] or loosely as van der Waals forces) are a type of intermolecular force acting between atoms and molecules that are normally electrically symmetric; that is, the electrons are ...
Van der Waals began work by trying to determine a molecular attraction that appeared in Laplace's theory of capillarity, and only after establishing his equation he tested it using Andrews' results. [35] [36] By 1877 sprays of both liquid oxygen and liquid nitrogen had been produced, and a new field of research, low temperature physics, had ...
Van der Waals forces originate from the interactions between induced, permanent or transient electric dipoles. In comparison with chemisorption , in which the electronic structure of bonding atoms or molecules is changed and covalent or ionic bonds form, physisorption does not result in changes to the chemical bonding structure.
Non-covalent interactions can be classified into different categories, such as electrostatic, π-effects, van der Waals forces, and hydrophobic effects. [3] [2] Non-covalent interactions [4] are critical in maintaining the three-dimensional structure of large molecules, such as proteins and nucleic acids.
Intermolecular forces such as Van der Waals forces, hydrogen bonds, and dipole–dipole interactions are typically not sufficiently strong to hold two apparently conformal rigid bodies together, since the forces drop off rapidly with distance, [2] and the actual area in contact between the two bodies is small due to surface roughness and minor imperfections.
The Van der Waals forces are effective only up to several hundred angstroms. When the interactions are too far apart, the dispersion potential decays faster than 1 / r 6 ; {\displaystyle 1/r^{6};} this is called the retarded regime, and the result is a Casimir–Polder force .
The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction.