Models for solvation

Qiu D, P S Shenl F P HoUinger and W C Still 1997. The GB/SA Continuum Model for Solvation. / Fast Anal5dical Method for the Calculation of Approximate Bom Radii. Journal of Physical Chcniistr 101 3005-3014. 

HyperChem uses the TIP3P water model for solvation.You can place the solute in a box of TIP3P water molecules and impose periodic boundary conditions. You may then turn off the boundary conditions for specific geometry optimization or molecular dynamics calculations. However, this produces undesirable edge effects at the solvent-vacuum interface. 

FIGURE 4.8. A surface constrained all-atom (SCAAS) model for solvated proteins. The figure depicts the different regions of the model around Asp 3 in the protein BPTI. Region a includes the solute atoms and the unconstrained protein atoms as well as the unconstrained water molecules. Region b is the surface constraints region which is surrounded by a bulk region (see Ref. 10 for more details). 

Fortunelli, A. and J. Tomasi. 1994. The implementation of density functional theory within the polarizable continuum model for solvation. Chem. Phys. Lett. 231, 34. 

S. C. Tucker and D. G. Truhlar, Generalized Bom fragment charge model for solvation effects as a function of reaction coordinate, Chem. Phys. Lett. 157 164 (1989). 

This chapter reviews models based on quantum mechanics starting from the Schrodinger equation. Hartree-Fock models are addressed first, followed by models which account for electron correlation, with focus on density functional models, configuration interaction models and Moller-Plesset models. All-electron basis sets and pseudopotentials for use with Hartree-Fock and correlated models are described. Semi-empirical models are introduced next, followed by a discussion of models for solvation. 

A number of theoretical models for solvation dynamics that go beyond the simple Debye Onsager model have recently been developed. The simplest is an extension of Onsager model to include solvents with a non-Debye like (dielectric continuum and the probe can be represented by a spherical cavity. Newer theories allow for nonspherical probes [46], a nonuniform dielectric medium [45], a structured solvent represented by the mean spherical approximation [38-43], and other approaches (see below). Some of these are discussed in this section. Attempts are made where possible to emphasize the comparison between theory and experiment. 

Besides the obvious practical importance of solvation dynamics in water, from a fundamental standpoint, water offers a unique opportunity to evaluate theoretical models for solvation. Only for water have extensive molecular dynamics simulations been accomplished (see below). Also semi-empirical models for solvation dynamics, such as MSA, can be carefully examined for water because the necessary information on the dielectric dispersion 2(high level of accuracy. The results of the solvation... 

Models for solvation in water that allow for a structured solvent do indeed predict a multiexponential response. For instance, the dynamical mean spherical approximation (MSA) for water solvation predicts that solvation of an ion in water is well represented by two characteristic times [38]. Nonetheless, the specific relaxation times differ substantially from the observed behavior [33],... 

J. Tomasi, G. Alagona, R. Bonaccorsi and C. Ghio, A theoretical model for solvation with some applications to biological sistems, in Z. B. Maksic (ed.), Modelling of Structure and Properties of Molecules, Ellis-Horwood, Chichester, 1987, p. 330. 

T. Vreven, B. Mennucci, C. O. da Silva, K. Morokuma and J. Tomasi, The ONIOM-PCM method Combining the hybrid molecular orbital method and the polarizable continuum model for solvation. Application to the geometry and properties of a merocyanine in solution, J. Chem. Phys., 115 (2001) 62-72. 

GB/SA Continuum Model for Solvation. A Fast Analytical Method for the Calculation of Approximate Born Radii. 

Qiu D, Shenkin PS, Hollinger FP, Still WC (1997) The GB/SA continuum model for solvation a fast analytical method for the calculation of approximate born radii, J Phys Chem A, 101 3005-3014... 

Sharp, K., Jean-Charles, J., and Honig, B. (1992) A local dielectric constant model for solvation free energies which accounts for solute polarizability, J. Phys. Chem. 96, 3822-3828. 

Hawkins, G. D. Cramer, C. J. Truhlar, D. G. Universal quantum mechanical model for solvation free energies based on gas-phase geometries, J. Phys. Chem. B 1998, 102, 3257-3271. 

Feng D-F, Kevan L. (1980) Theoretical models for solvated elctrons. Chem Rev 80 1-20. 

K. Sharp, A. Jean-Charles, and B. Honig, /. Phys. Chem., 96, 3822 (1992). A Local Dielectric Constant Model for Solvation Free Energies Which Accounts for Solute Polarizability. 

D. J. Giesen, C. J. Cramer, and D. G. Truhlar,/. Phys. Chem., submitted for publication. A Semiempirical Quantum Mechanical Solvation Model for Solvation Free Energies in All... 

The solvation structures which we have determined for the supercritical solutions of LJ molecules appear to be in agreement with the recent theoretical and experimental suggestions of solvent-solute clustering and solute-solute aggregation near the CP. Quantitative testing of theoretical models for solvation structure of supercritical solutions (such as that presented here) may become possible if recent efforts at simulation of supercritical solutions (elsewhere in this volume) prove successful. Clearly, the LJ model used in our theoretical studies to date does not provide an adequate representation of real molecular interactions. However, the method we have demonstrated is potentially capable of application with much more accurate (and complicated) potential functions, and meaningful quantitative interpretation of experiments may then become possible. 

Davis, M. E. (1994). The inducible multipole solvation model-a new model for solvation effects on solute electrostatics. J. Chem. Phys. 100 5149-59. 

Among the many approximate models for solvation free energy evaluation, the most frequently used is the generalized Born (GB) model. It evaluates the solvation energy using the following equation ... 

Chen W, Gordon MS. The effective fragment model for solvation internal rotation in formamide. J Chem Phys 1996 105 11081-11090. 

UV and visible studies tend not to give much direct information about the interatomic stmcture since the details of the stmcture tend to require a particular model for solvation to be assumed first. However, they are excellent for probing the possible symmetries of the chosen ion in solution. These techniques are of particular importance and use for transition metal ions. 

Smithrud, D.B. Diederich. F. Strength of molecular complexation of apolar solutes in water and in organic solvents is predictable by linear free energy relationships A general model for solvation effects on apolar binding. J. Am. Chem. Soc. 1990. 772. 339-343. 

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