Molecular solvent model

Torrie, G. M. and Patey, G. N. Molecular solvent model for an electrical double layer asymmetric solvent effects, J.Phys.Chem., 97(1993). 12909-12918... 

Simonson T. Free Energy Calculations. In Computational Biochemistry and Biophysics Becker OM, MacKerellm AD, Roux B, Watanabe M, eds. 2001. Marcel Dekker Inc., New York. Leontyev FV, Basilevsky MV, Newton MD. Theory and computation of electron transfer reorganization energies with continuum and molecular solvent models. Theor. Chem. Acc. 2004 111 110-121. 

G. M. Torrie and G. N. Patey, /. Phys. Chem., 97,12909 (1993). Molecular Solvent Model for an Electrical Double Layer Asymmetric Solvent Effects. 

Computation of Direct Effects - Molecular Solvent Model... 

Specific solute-solvent interactions involving the first solvation shell only can be treated in detail by discrete solvent models. The various approaches like point charge models, siipennoleciilar calculations, quantum theories of reactions in solution, and their implementations in Monte Carlo methods and molecular dynamics simulations like the Car-Parrinello method are discussed elsewhere in this encyclopedia. Here only some points will be briefly mentioned that seem of relevance for later sections. 

The explicit definition of water molecules seems to be the best way to represent the bulk properties of the solvent correctly. If only a thin layer of explicitly defined solvent molecules is used (due to hmited computational resources), difficulties may rise to reproduce the bulk behavior of water, especially near the border with the vacuum. Even with the definition of a full solvent environment the results depend on the model used for this purpose. In the relative simple case of TIP3P and SPC, which are widely and successfully used, the atoms of the water molecule have fixed charges and fixed relative orientation. Even without internal motions and the charge polarization ability, TIP3P reproduces the bulk properties of water quite well. For a further discussion of other available solvent models, readers are referred to Chapter VII, Section 1.3.2 of the Handbook. Unfortunately, the more sophisticated the water models are (to reproduce the physical properties and thermodynamics of this outstanding solvent correctly), the more impractical they are for being used within molecular dynamics simulations. 

The substituted hydroxylamine C NOPP from reaction 7) can take part in various dark reactions, even at ambient temperature. From a study of the low molecular weight model I in the liquid phase, two decomposition pathways are possible (reaction 8) (12). The products from the disproportionation reaction 8a were only observed in the absence of a radical trap such as O2. In a given solvent ks kaa-Uo (solvent air saturated and degassed respectively). Both k8a and ke were found to increase by an order of magnitude on going from a non-polar solvent (iso-octane) to a polar solvent (methanol or tert.-butyl hydro peroxide, BuOOH). 

A molecular orbital model (MO) treats all electrons belonging to a fixed number of solvent molecules plus an excess electron in the resultant field of the nuclei of the molecules as being in a fixed configuration. The nuclei belonging to a particular molecule normally keep the ground state structure of that molecule. The relative distances and orientations of these molecules are varied until energetic, and if possible configurational, stability is obtained. In some cases, molecular distortions have been considered. 

Quantum chemical methods are well established, accepted and of high potential for investigation of inorganic reaction mechanisms, especially if they can be applied as a fruitful interplay between theory and experiment. In the case of solvent exchange reactions their major deficiency is the limited possibility of including solvent effects. We demonstrated that with recent DFT-and ab initio methods, reaction mechanisms can be successfully explored. To obtain an idea about solvent effects, implicit solvent models can be used in the calculations, when their limitations are kept in mind. In future, more powerful computers will be available and will allow more sophisticated calculations to be performed. This will enable scientists to treat solvent molecules explicitly by ab initio molecular dynamics (e.g., Car-Parrinello simulations). The application of such methods will in turn complement the quantum chemical toolbox for the exploration of solvent and ligand exchange reactions. 

Desolvation free energies are computed using either explicit solvent or an implicit solvent model. While explicit solvent simulations are usually considered more accurate or at least more representative of the true molecular environment, simulations using implicit solvent are often chosen... 

An accurate quantitative prediction of their relative affinities by a combination of molecular mechanics and continuum solvent models, J. Med. Chem. 43 3786 (2000). 

Table 7 compares free energies of hydration125 produced by the two types of solvent models that have been presented discrete molecular and continuum. The discrete molecular involved classical force field molecular dynamics (MD) and a free energy perturbation (FEP) technique whereby the solute molecule is annihilated to dummy atoms, so that absolute AGhydration are obtained the continuum were SCRF/PCM calculations, with Claverie-Pierotti Gcavilatlon and Floris-Tomasi Gvdw. The... 

Free Energies of Hydration Predicted by Discrete Molecular (MD/FEP) and Continuum (SCRF/PCM) Solvent Models, in kcal/mole.g... 

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