Dipolar interaction, induced

Toukmaji A, Sagui C, Board J, Darden T (2000) Efficient particle-mesh Ewald based approach to fixed and induced dipolar interactions. J Chem Phys 113(24) 10913—10927... 

Induced dipolar interactions. The electron clouds in many (especially large) organic molecules are readily polarised resulting in the formation of induced dipoles that can interact, resulting in complex stabilisation. Both cations and anions can induce dipoles in aromatic molecules, for example. 

In addition to the repulsive electrostatic interactions, two isolated identical particles immersed in a solvent of different index of refraction, experience an attractive interaction, namely, the van der Walls or dispersion forces, which arise from the induced dipolar interactions between the molecules constituting the two particles. This interaction depends on the geometry (the shape of the particles) and on the material of which the particles are made of. For two spherical particles, the van der Waals interparticle potential uyj(r) is given by... 

Efficient Particle-Mesh Ewald Based Approach to Fixed and Induced Dipolar Interactions. 

As the bromine molecule approaches the n electrons, they induce a temporary dipole in the electron cloud of the bromine. This is easily done, because the outer electrons on the bromine molecule are a long way from the two positive nuclei, and so are held less firmly than if they were more closely bound. In other words, the bromine molecule is a soft electrophile, because its electron cloud may be easily distorted. Note that all temporarily induced dipolar interactions are attractive in nature, and so facilitate the further approach of the reacting species. 

Toukmaji, A., Sagui, C., Board, J. A., and Darden, T. (2000). Efficient PME-based approach to fixed and induced dipolar interactions,/. Chem. Phys. 113, pp. 10913-10927. 

Dipolar and induced dipolar interactions cause this general and fundamental attractive interaction. The character of this interaction is comparatively weak and comparatively long-range in order. The interaction is, in principal, proportional to the refractive index difference between the phases. The difference between oil and water is large and only fairly high concentrations of dissolved material reduce the van der Waals interactions significantly. 

The interactions generally grouped together as van der Waals forces will then be covered more or less in order of increasing complexity—that is, interactions of permanent dipoles, induced dipolar interactions, and finally the quantum mechanical forces. 

From comparison of the optical properties of particles deposited on the same substrate and differing by their organization (Figs. 7 and 8) it can be concluded that the appearance of the resonance peak at 3.8 eV is due to the self-organization of the particles in a hexagonal network. This can be interpreted in terms of mutual dipolar interactions between particles. The local electric field results from dipolar interactions induced by particles at a given distance from each other. Near the nanocrystals, the field consists of the ap-... 

Fig. 9.5 Illustration of the dipolar interaction. (A and B) The magnetic field induced by spin I adds up to the static magnetic field Bo and leads to a shift of the resonance frequency of the close-by spin S. Since spins parallel and...

The outer shell of each atom in CI2 possesses a full octet of electrons seven electrons of its own (which explains why it belongs to Group VII(b) of the periodic table) and an extra electron from covalent sharing with the other atom in the CI2 molecule. The only other simple interactions in molecular chlorine are the inevitable induced dipolar forces, which are too weak at room temperature to allow for the liquefying of Cl2(g). 

Van der Waals forces are intermolecular and are classified as (i) dipole-dipole interactions, (ii) dipole-induced-dipole interactions and (iii) London dispersion forces which operate between atoms as the result of the nucleus not always being at the centre of mass of the surrounding electrons. The hydrogen bond is regarded as a special form of dipole-dipole interaction, because the positive end of dipolar species containing hydrogen atoms is the relatively unshielded proton. 

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