Implicit solvation scheme

You can conduct your reaction experiment in a solution-like environment. One of the options in the set-up window of a program is to let you to turn on an implicit solvation model (48). Such models attempt to account for the mutual interaction of the dipoles of the water molecules and the electron distribution in the solute molecule, as well as to account for the energy required to create a cavity in the bulk solvent to accommodate the solute. A very dilute solution is assumed, so the solute molecules do not see each other. Several implicit solvation modeling schemes have been proffered in the literature and are incorporated in various quantum mechanical programs. 

For reactions in solution, one may implement explicit or implicit hydration schemes. In explicit hydration, water molecules are included in the system. These additional water molecules have a significant effect on the reaction coordinates of a reaction (e g., Felipe et al. 2001). Implicit hydration schemes, or dielectric continuum solvation models (see Cramer and Truhlar 1994), refer to one of several available methods. One may choose between an Onsager-type model (Wong et al. 1991), a Tomasi-type model (Miertus et al. 1981 Cances et al. 1997), a static isodensity surface polarized continuum model or a self consistent isodensity polarized continuum model (see Frisch et al. 1998). 

With Monte Carlo methods, the adoption of the Metropolis sampling scheme intrinsically assumes equilibrium Boltzmann statistics, so special modifications are required to extend MC methods to non-equilibrium solvation as well. Fortunately, for a wide variety of processes, ignoring non-equilibrium solvation effects seems to introduce errors no larger than those already inherent from other approximations in the model, and thus both implicit and explicit models remain useful tools for studying chemical reactivity. 

The differences between the Nancy and Badajoz approaches are related to the different general strategies of the solvation procedures followed by the two groups. We shall comment later the whole SCRF computational scheme developed by Rivail and coworkers. Here we limit ourselves to say that they use multipolar expansions. The multipole approach implicit in... 

Dissolution reactions, for example, need to take into account the surrounding water molecules. In conventional MO-TST, one may use larger clusters and any of the two hydration schemes. An alternative is a periodic slab to model a crystal surface, explicitly adorned with water molecules and optionally given an implicit hydration treatment. The significance of applying these continuum solvation methods on MO-TST studies has not been well established in geochemistry. 

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