Quantum mechanical calculation of thermodynamic functions of solvation of ammonium ions in water

Abstract

The application of an extended version of the generalized Born formula including dielectric saturation effects, implemented within the SCF-CNDO/2 approximation, provides a complete set of data concerning the thermodynamics of solvation of some ammonium ions in water. The calculated free energies of solvation are in good agreement with experimental data. An estimation of the entropy and enthalpy of solvation is also given and satisfactory qualitative trends are obtained.

Cation−π and π–π Interactions in Aqueous Solution Studied Using Polarizable Potential Models

“…As a control for the “hybrid residue” method used (see Section 2.2.3), the change in free energy for mutating Na + to K + is also calculated and compared to published values obtained using a different protocol . The results are reported in Table , along with corresponding experimental and computational data. − On the basis of multiple runs (forward and backward), the error on the calculated values is of the order of 0.1 kcal/mol.…”

On theSCF theory of continuum solvent effects representation II. Quantum chemical calculation of thermodynamic properties of some acid-base equilibria in solution

“…An improvement of the description of the solvation entropy has been obtained with respect to our previous work [18]. This result is probably due to the more correct description of the solvent polarization together with the rigorous thermodynamic relationships used.…”

“…The internal polarization charge-electron interaction integrals, y i E , were calculated according to the parametrization scheme previously reported [ 171: For AOS associated with the same atomic center yXA is given by 1/rA, where rA is Pauling's van der Waals radius of the particular atom [18]. When the AO and the internal polarization charges are associated with different atomic centers, A and B, say, the internal solute-solvent interactions were calculated as where R A B is the interatomic distance.…”

New developments in the continuum representation of solvent effects

“…As mentioned above, the spherical analogue of eq 36 overestimates the solvation free energy, given that the atoms of the solute are implicitly considered as lying in separate cavities. 34 Now, we shall allow for the steric inhibition to solvation due to the specific neighborhood of each atomic center of the solute (SCRF/O scheme). Even when the general formalism and its application to the spherical case is in the literature,35•36,42,43 its application to the case treated here is not direct.…”

“…The superscript i in the TAB's refers to the interaction integrals of the solute with the polarization charges located on the ith surface. They can be evaluated according to the parametrization suggested by Miertus and Kysel,46 enlarged by Contreras,34 and generalized here as follows:…”