Dispersion repulsion energy

Among the alternative definitions of the dispersion-repulsion energy, we mention the quantum mechanical approach presented in ref. [12], which has the merit of including this part of the nonelectrostatic contribution in the molecular Hamiltonian (like the electrostatic term), so that the solvent affects not only the free energy but also the electronic distribution. In this approach, however, the dispersion part is highly expensive except for very small systems, and it is not routinely used in any computational package the analytical derivatives of quantum mechanical /disp rep can be derived but they have not been implemented until now. 

The heats of sorption of ethane and propane in silicalite are some 5r6 kJ mof greater than the corresponding heats in NaY. The Na cations present in and Sm sites of the supercages of NaY introduce a polarization energy contribution to these heats of soiption of hydrocarbons in NaY but this contribution is smaller than the increase in the net dispersion-repulsion energy in silicalite due to the closer fit of these molecules in die smaller channels and intersections in this latter framework. In the case of the smaller CH molecule the difference is... 

Analytieal expressions for the three terms (eleefrostatie, polarization and dispersion-repulsion energies) are obtained from the intermoleeular interactions theory. 

A scheme has been developed that reduces the spatial representation of the dispersion interaction into a surface representation of this interaction. According to this approach, the average dispersion-repulsion energy of a solute-solvent system has been written as follows ... 

The dispersion-repulsion energy arising between a polarizable solute and the solvent molecules of finite size, which is always a negative contribution. 

When two or more molecular species involved in a separation are both adsorbed, selectivity effects become important because of interaction between the 2eobte and the adsorbate molecule. These interaction energies include dispersion and short-range repulsion energies (( ) and ( )j ), polarization energy (( )p), and components attributed to electrostatic interactions. 

The crystal field effect is due primarily to repulsive effects between electron clouds. As we have already seen, the repulsive energy is of opposite sign with respect to coulombic attraction and the dispersive forces that maintain crystal cohesion. An increase in repulsive energy may thus be interpreted as actual destabilization of the compound. 

Particles in all kinds of suspensions or dispersions interact with two different kinds of forces (e.g., attractive forces and repulsive forces). One observes that, lyophobic suspensions (sols) must exhibit a maximum in repulsion energy in order to have a stable... 

The simplest functional form tliat tends to be used in force fields to represent the combination of the dispersion and repulsion energies is... 

Coulomb energy repulsion energy dispersion energy zero point energy... 

Diphenyimethane and diphenylamine are iso-electronic, and there is every reason to suppose they would have closely similar dispersion and repulsion energy terms, but the difference (23-08-15-3) = 7-8 kcal/mole includes probably a number of contributions above those... 

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