Dispersion energies, between solvent

The Self-Consistent Reaction Field (SCRF) model considers the solvent as a uniform polarizable medium with a dielectric constant of s, with the solute M placed in a suitable shaped hole in the medium. Creation of a cavity in the medium costs energy, i.e. this is a destabilization, while dispersion interactions between the solvent and solute add a stabilization (this is roughly the van der Waals energy between solvent and solute). The electric charge distribution of M will furthermore polarize the medium (induce charge moments), which in turn acts back on the molecule, thereby producing an electrostatic stabilization. The solvation (free) energy may thus be written as... 

McMillan-Mayer theory of solutions [1,2], which essentially seeks to partition the interaction potential into tln-ee parts that due to the interaction between the solvent molecules themselves, that due to die interaction between the solvent and the solute and that due to the interaction between the solute molecules dispersed within the solvent. The main difference from the dilute fluid results presented above is that the potential energy u(r.p is replaced by the potential of mean force W(rp for two particles and, for particles of solute in the solvent, by the expression... 

Coarse-grained molecular d5mamics simulations in the presence of solvent provide insights into the effect of dispersion medium on microstructural properties of the catalyst layer. To explore the interaction of Nation and solvent in the catalyst ink mixture, simulations were performed in the presence of carbon/Pt particles, water, implicit polar solvent (with different dielectric constant e), and ionomer. Malek et al. developed the computational approach based on CGMD simulations in two steps. In the first step, groups of atoms of the distinct components were replaced by spherical beads with predefined subnanoscopic length scale. In the second step, parameters of renormalized interaction energies between the distinct beads were specified. 

As a result, some approaches to computing dispersion energy have involved using either experimental or theoretical data for gas-phase clusters to estimate the strength of dispersion interactions between different possible solute and solvent functional groups. However,... 

The nonpolar solvation free energy is given by the sum of two terms the free energy to form the cavity in solvent filled by the solute and the dispersion attraction between solute and solvent [65,113]. The nonpolar free energy is written as [27]... 

U = molar internal energy Fm = molar volume T = absolute temperature). This small expansion does not necessarily disrupt all the intermolecular solvent-solvent interactions. The internal pressure results from the forces of attraction between solvent molecules exceeding the forces of repulsion, i.e. mainly dispersion and dipole-dipole interactions cf. Table 3-2). 

In section II we focused on an accurate description of electrostatic interactions between solute and solvent. Although these interactions accormt for the largest parts of the free energy of solvent, other interactions may contribute as well. These interactions, due to dispersion and repulsion, were studied by Curutchet et al Amoville and Mennucci had earlier developed a formalism for including these interactions in the polarizable continuum model and Curutchet et al. tested it on a larger set of solvent-solute systems for which they also calculated these interactions with force-field methods. 

The interactions between molecules which produce the cohesive energy characteristic of the liquid phase are described in the section entitled Secondary Forces Between Solvent and Solute Molecules. These involve the dispersion forces, dipole-dipole and dipole-induced dipole interactions, and specific interactions, especially hydrogen bonding. If it is assumed that the intermolecular forces are the same in the vapor and liquid states, then -E is the energy of a liquid relative to its ideal vapor at the same temperature. It can be described as the energy required to vaporize 1 mole of liquid to the saturated vapor phase (Af U) plus the energy required for the isothermal expansion of the saturated vapor to infinite volume. Detailed discussion of the theory and derivations is given in the publications by Hildebrand and associates cited above. 

---