Dispersion energy interactions

For the case of two spherical particles of radii ax and a2, separated in vacuo by a shortest distance H, Hamaker197 derived the following expression for the London dispersion interaction energy, VA ... 

It was mentioned earlier that the dispersion interaction energy (DIS) is the most important attractive term of the correlation energy (CORR) it is usually attributed to the van der Waals interactions, physical meaning of the latter is usually the sum of attraction (DIS) and the repulsive exchange energy (EX). 

If we neglect the difference between electrostatic and dispersion interaction energies, then, in accordance with the concept of volume filling of micropores described previously, the equation of adsorption of methane on zeolite L will be expressed by Ref. 3 as... 

The reference state is taken to be the chemical potential and vapor pressure of the bulk lubricant m(oo) = 0 and P°(oo) is the vapor pressure of the bulk liquid. The surface chemical potential is approximated by the unretarded atom-slab dispersive interaction energy ... 

J.K. Jenkins, A. Salam, T. Thirunamachandran, Retarded Dispersion Interaction Energies Between Chiral Molecules. Phys. Rev. A 50 (1994) 4767. 

Equation (532) shows the net dispersion interaction energy for a sphere at a distance D away from the surface of the plane solid, if the additivity principle is assumed. There are... 

Dispersion force The dispersion or London force arises from the instantaneous transient dipoles that all molecules possess as a result of the changes in the instantaneous positions of electrons. The dispersion force which in fact is an induced dipole-induced dipole interaction depends on the polarizability of the interacting molecules and is inversely proportional to the sixth power of separation. In the case of, e.g., two CH4 molecules at a separation of 3 A, the dispersion interaction energy is of the order of — 1.1 kcal/mol. 

Calculate the dispersion interaction energy at 500 pm separation between two molecules of... 

The second approach for the evaluation of the repulsion and dispersion interaction energy allows to introduce these contributions in the the effective Hamiltonian through the solvnt reaction potential (1.5) and to evaluate their effects on the QM description and on the properties of the solute. 

The component 6 of solubility parameter includes dispersive interactions energy and dipole bonds interaction energy and the component 6 - hydrogen bonding interaction and the interaction energy between an electron-rich atom of one molecule (donor) and an electron-deficient atom of another molecule (acceptor), which requires a certain orientation of these two molecules. In such treatment there is no need to introduce a separate component for interaction between polar molecules description. 

For most substances, the retardation effect in the dispersion interaction energy becomes significant at distances greater than 100 A. The important point is that the Hamaker constant A defined in Eq. (167) is no longer constant but depends on the separation of interacting bodies. 

The van der Waals energy for two flat plates separated by distance R is given by Eqs. (168) and (169), and that for two identical spherical bodies of radius a is given by Eq. (170). For the case of two spherical shells, the expression for the dispersion interaction energy is given elsewhere. ... 

In our DFT-D applications, the dispersion term, limited to the dipole-dipole contribution to the dispersion interaction energy. 

Interestingly, it had been suggested that the dispersion interaction energy between the solute and the solvent eould be accounted for, in principle, in the framework of this approach as related to the full distribution of dielectric relaxation frequencies of the solvent. Thus, the formula for the MC SCRF solvation energy has been expressed as follows... 

The dispersion interaction energy between two identical atoms or molecules having distance r apart is governed by the following London s equation ... 

Quantum mechanical calculations were also applied to evaluate the nature of the weak interactions between atoms. These weak interactions are responsible for the induced dipole cohesion of neutral atoms. It has been shown that the dispersion interaction energy of two atoms or ions with closed electronic configurations varied according to their polarizability and ionization energies. London used perturbation theory to obtain a simplified expression for the dispersion energy, Ejj, of two interacting species i and /, at separation r. 

Hohm U (1994) Dispersion of polarizability anisotropy of H2, O2, N2O, CO2, NH3, C2H6, and cyclo-C3H6 and evaluation of isotropic and anisotropic dispersion-interaction energy coefficients. Chem Phys 179 533-541... 

---