Quantum mechanics solvation, free energy

This approach may be possible for small molecules because the gas-phase proton affinity can be obtained quantum mechanically with an accuracy of 1-2 kcal/mol [19]. However, the solvation free energy of H+ cannot be calculated and the experimental value is only known approximately, from 259.5 to 262.5 kcal/mol [60]. Also, because the proton affinity and solvation free energies in Eq. (10-7) are on the order of hundreds of kcal/mol, small percentage errors in the calculation can give rise to large error in AGaqP and pKa. Thus, this method for calculation of absolute pifa s remains impractical at the present time [6],... 

Vaidehi, N., Wesolowski, T. A. and Warshel, A. J. Quantum-mechanical calculations of solvation free energies. A combined ab initio pesudopotential free-energy perturbation approach, J. Chem.Phys.,91... 

Giesen, D. J., Storer, J., Cramer, C. J. and Truhlar, D. J. General semiempirical quantum mechanical solvation model for nonpolar solvation free energies, n-hexadacane., J.Am. Chem.Soc., 117 (1995), 1057-1068... 

Quantum-Mechanical Electrostatic Solvation Free Energy... 

C. Curutchet, M. Orozco, F. J. Luque, B. Mennucci and J. Tomasi, Dispersion and repulsion contributions to the solvation free energy comparison of quantum mechanical and classical approaches in the polarisable continuum model, J. Comput. Chem. 27 (2006) 1769-1780. 

To the quantum mechanical contribution to the solvation free energy (4) it is also necessary to add the work required to create the cavity in which the solute is placed this quantity, namely the cavitation free energy, is calculated with the Pierotti-Claverie formula [16, 17]. 

The atomic radii may be further refined to improve the agreement between experimental and theoretical solvation free energies. Work on this direction has been done by Luque and Orozco (see [66] and references cited therein) while Barone et al. [67] defined a set of rules to estimate atomic radii. Further discussion on this point can be found in the review by Tomasi and co-workers [15], It must be noted that the parameterization of atomic radii on the basis of a good experiment-theory agreement of solvation energies is problematic because of the difficulty to separate electrostatic and non-electrostatic terms. The comparison of continuum calculations with statistical simulations provides another way to check the validity of cavity definition. A comparison between continuum and classical Monte Carlo simulations was reported by Costa-Cabral et al. [68] in the early 1980s and more recently, molecular dynamics simulations using combined quantum mechanics and molecular mechanics (QM/MM) force-fields have been carried out to analyze the case of water molecule in liquid water [69],... 

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. 

A General Semiempirical Quantum Mechanical Solvation Model for Nonpolar Solvation Free Energies. n-Hexadecane. 

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... 

Cummins PL, Gready JE. Coupled semiempirical quantum mechanics and molecular mechanics (QM/MM) calculations on the aqueous solvation free energies of ionized molecules. J Comput Chem 1999 20 1028-1038. 

For many chemical problems, it is crucial to consider solvent effects. This was demonstrated in our recent studies on the hydration free energy of U02 and the model reduction of uranyl by water [232,233]. The ParaGauss code [21,22] allows to carry out DKH DF calculations combined with a treatment of solvent effects via the self-consistent polarizable continuum method (PCM) COSMO [227]. If one aims at a realistic description of solvated species, it is not sufficient to represent an aqueous environment simply as a dielectric continuum because of the covalent nature of the bonding between an actinide and aqua ligands [232]. Ideally, one uses a combination model, in which one or more solvation shells (typically the first shell) are treated quantum-mechanically, while long-range electrostatic and other solvent effects are accounted for with a continuum model. Both contributions to the solvation free energy of U02 were... 

N. Vaidehi, T. A. Wesolowski, and A. Warshel, /. Chem. Phys., 97,4264 (1992). Quantum-Mechanical Calculations of Solvation Free Energies. A Combined ah initio Pseudopotential Free-Energy Perturbation Approach. 

Validation of the OPLS2.0 force field includes comparison to quantum mechanical energy profiles and experimental solvation free energies. For the latter, we performed explicit solvent molecular dynamics free energy perturbation simulations on a set of 239 diverse small molecules [80]. Compared with other popular force fields... 

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