Editing Intermolecular force (section)

===Debye force (permanent dipoles–induced dipoles) {{Anchor|Debye force}}===
The second contribution is the induction (also termed polarization) or Debye force, arising from interactions between rotating permanent dipoles and from the polarizability of atoms and molecules (induced dipoles). These induced dipoles occur when one molecule with a permanent dipole repels another molecule's electrons. A molecule with permanent dipole can induce a dipole in a similar neighboring molecule and cause mutual attraction. Debye forces cannot occur between atoms. The forces between induced and permanent dipoles are not as temperature dependent as Keesom interactions because the induced dipole is free to shift and rotate around the polar molecule. The Debye induction effects and Keesom orientation effects are termed polar interactions.<ref name=j1/>

The induced dipole forces appear from the induction (also termed [[Dipolar polarization|polarization]]), which is the attractive interaction between a permanent multipole on one molecule with an induced (by the former di/multi-pole) 31 on another.<ref name=Blustin-1978>{{Cite journal |doi= 10.1007/BF00577166 |title= A Floating Gaussian Orbital calculation on argon hydrochloride (Ar·HCl) |journal= Theoretica Chimica Acta |volume= 47 |issue= 3 |pages= 249–257 |year= 1978 | vauthors = Blustin PH |s2cid= 93104668 }}</ref><ref name=Roberts-Orr-1938>{{Cite journal |doi= 10.1039/TF9383401346 |title= Induced dipoles and the heat of adsorption of argon on ionic crystals |journal= Transactions of the Faraday Society |volume= 34 |pages= 1346 |year= 1938 | vauthors = Roberts JK, Orr WJ }}</ref><ref name=Sapse-et-al-1979>{{Cite journal |doi= 10.1038/278332a0 |title= Ion-induced dipole H−n clusters |journal= Nature |volume= 278 |issue= 5702 |pages= 332–333 |year= 1979 | vauthors = Sapse AM, Rayez-Meaume MT, Rayez JC, Massa LJ |bibcode= 1979Natur.278..332S|s2cid= 4304250 }}</ref> This interaction is called the ''Debye force'', named after [[Peter J. W. Debye]].

One example of an induction interaction between permanent dipole and induced dipole is the interaction between HCl and Ar. In this system, Ar experiences a dipole as its electrons are attracted (to the H side of HCl) or repelled (from the Cl side) by HCl.<ref name=Blustin-1978/><ref name=Roberts-Orr-1938/> The angle averaged interaction is given by the following equation:

:<math>\frac{-d_1^2 \alpha_2}{16\pi^2 \varepsilon_0^2 \varepsilon_r^2 r^6} = V,</math>

where <math>\alpha_2</math> = polarizability.

This kind of interaction can be expected between any polar molecule and non-polar/symmetrical molecule. The induction-interaction force is far weaker than dipole–dipole interaction, but stronger than the [[London dispersion force]].