Debye induction forces

Debye Induction Forces. These forces result from interaction between permanent and induced dipoles. 

Van der Waals postulated that neutral molecules exert forces of attraction on each other which are caused by electrical interactions between dipoles. The attraction results from the orientation of dipoles due to any of (1) Keesom forces between permanent dipoles, (2) Debye induction forces between dipoles and induced dipoles, or (3) London-van der Waals dispersion forces between fluctuating dipoles and induced dipoles. (The term dispersion forces arose because they are largely determined by outer electrons, which are also responsible for the dispersion of light [272].) Except for quite polar materials the London-van der Waals dispersion forces are the more significant of the three. For molecules the force varies inversely with the sixth power of the intermolecular distance. 

Debye inductive force induced dipole-permanent dipole interaction [43,44]. 

For a pair of identical molecules, it is noted in Eq. (13) that the first term determined with regard to the deformation polarizability is a so-called Debye inductive force , and the second term is generally called a Keesom orientational force between molecules when the dipole moment is considered in the intermolecular attractive system. 

In the case of physical bonds (London dispersion, Keesom orientation, and Debye induction forces), the energy of interaction or reversible energy of adhesion can be directly calculated from the surface free energies of the solids in contact. 

Dispersion Forces The dipolar interaction forces between any two bodies of finite mass, including the Keesom forces of orientation among dipoles, Debye induction forces, and London forces between two induced dipoles. Also referred to as Lifshitz—van der Waals forces. 

Weak, secondary forces, resulting from molecular dipoles, also act between materials. They are often classified according to the nature of the interacting dipoles. Keesom orientation forces act between permanent dipoles, London dispersion forces between transient dipoles, and Debye induction forces between a permanent and an induced dipole, see O Tables 2.1 and O 2.2. These are collectively known as van der Waals forces (but note alternative usage of this term, O Table 2.2), and occur widely between materials. They are much less dependent upon specific chemical structure than primary bonds. Indeed, dispersion forces are universal. They only require the presence of a nucleus and of extranuclear electrons, so they act between all atomic and molecular species. 

To reflect the contribution of the fundamental nature of the long-range interaction forces across the interface, it was suggested (Fowkes 1964) that surface free energies and work of adhesion may be expressed (O Eq. 3.11) by the sum of two terms the first one representative of London s dispersion interactions (superscript D) and the second representative of nondispersion forces (superscript ND), this latter include Debye induction forces, Keesom orientation forces, and acid—base interactions. 

Induction forces, the so-called Debye forces ind> occur in the interaction between a permanent dipole of a solute or a polar solvent and an induced dipole in another compound. They are weak and appear during the analysis of the nonpolar polarized compounds, such as those with multiple... 

Dipole-induced dipole (free rotation/Debye or induction force) ... 

If no ion is present in the system (q, = 0) then the above expression gives the sum of the Keesom-dipolar orientation and Debye-induction contributions to the total van der Waals forces between two molecules. A third contribution to van der Waals forces is also present,... 

As we have seen, London dispersion interactions, Keesom dipole-dipole orientation interactions and Debye dipole-induced dipole interactions are collectively termed van der Waals interactions their attractive potentials vary with the inverse sixth power of the intermol-ecular distance which is a common property. To show the relative magnitudes of dispersion, polar and induction forces in polar molecules, similarly to Equation (78) for London Dispersion forces, we may say for Keesom dipole-orientation interactions for two dissimilar molecules using Equation (37) that... 

Induction Forces Debye forces. See Dispersion Forces. 

Debye-Falkenhagen-type forces do not suffer from the vanishing of the rotationally averaged interaction since they arise from a force due to induction which can track the rotation of the particle. Unlike the Keesom force in which, in principle, the interaction of distributed point charges are considered, induction forces are dependent upon a collective molecular or material property, the static dielectric constant. Definition of the domain of validity for the classical calculation is required and has been given in the case of metals [5.17]. Those authors pointed out that if the surface of the metal were taken at the center of mass of the surface charge distribution, then classical electrostatic calculations would be valid. 

Table 59.3 is based primarily on the Zisman critical surface tension of wetting and Owens and Wendt approaches because most of the polymer data available is in these forms. The inadequacies of equations such as Eq. (59.7) have been known for a decade, and newer, more refined approaches are becoming established, notably these of van Oss and coworkers [24]. A more limited number of polymers have been examined in this way and the data (at 20 °C) are summarized in Table 59.4. is the component of surface free energy due to the Lifshitz-van der Waals (LW) interactions that includes the London (dispersion, y ), Debye (induction), and Keesom (dipolar) forces. These are the forces that can correctly be treated by a simple geometric mean relationship such as Eq. (59.6). y is the component of surface free energy due to Lewis acid-base (AB) polar interactions. As with y and yP the sum of y and y is the total solid surface free energy, y is obtained from... 

Polar forces Debye induction Permanent/induced... 

The origin of forces between neutral symmetrical molecules, such as hydrogen (H2) or the inert gases (e.g. A, Ne), is not obvious. Because of the symmetry of the electron configuration, there cannot be any permanent dipole so, there can be neither dipole-dipole interactions (Keesom orientation interactions) nor dipole-molecule interaction (Debye induction interactions) (see Polar Forces). Further, there appears to be no Coulombic electrostatic interaction since they are electronically neutral overall, nor can there be any covalent bonding. Yet, there must be forces of some type between these molecules as the existence of liquid and solid hydrogen and argon demonstrate. 

Now let us examine the term of attraction. The force of attraction is due to three different physical effects the Keesom orientation effect, the Debye induction effect and the London dispersion effect. 

The form of interaction functiorrs such as those of Lennard-Jones, based on the model of Van der Waals forces irrvolving Keesom orientation effects, Debye induction and Lorrdon dispersion, which quickly decrease with distance beyorrd a certain distance between two molecules, the interaction can be negligible (for example, when the interaction is less than 5q/100)-This comes down to defming around each molecule a volume influence ... 

The molecular forces consist of three essentially different partSt of which two> the Keesom directional effect and the Debye induction effect, have been investigated earlier [muiaiia mutandis]. As the third part we have the interaction of the fast periodic mutual perturbation of the inner electronic motions in the molecule, which represents the mun portion of the molecular attraction for the most simple non-polar and weakly polar molecules. Especially, the assumption of the quadrup>ole structure of the noble gases, which was unavoidable up to now, is made superfluous. The purely theoretical determination of the molecular forces, which have to be treated as perturbational effects of second order, is hardly manageable. Instead the forces can be estimated ffom optical measurements through their theoretical relation with the /-values of the dispersion formula. The forces estimated in this way yield within the accuracy with which they have been established, the attraction part of the van der Waals equation of state. 

Induction Forces. Another polar interaction is the induction between a permanent dipole and an induced dipole . The energy for this type of polar interaction (Debye) between molecules is expressed... 

Vy = o = zero-frequency contribution due to polar/ induction forces (Keesom/Debye) ... 

Debye forces (or induction forces) correspond to the mutual attraction of a permanent dipole and the dipole that it induces on a nearby polarizable molecular group ... 

The first hint that there are non-covalent interactions between uncharged atoms and molecules came from the observations of van der Waals (1873, 1881). These interactions came to be known as van der Waals forces. The interactions responsible for these became clear with the work of Keesom (1915, 1920, 1921), Debye (1920, 1921) and London (1930) as, respectively, interactions between two permanent dipoles (orientation forces), a permanent dipole and an induced dipole (induction forces) and a fluctuating dip>ole and an induced dipole (dispersion forces). While these three kinds of interaction have different origins, the interaction energies for all three vary as the inverse of the distance raised to the sixth power ... 

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