Reaction field methods

Onsager s original reaction field method imposes some serious lunitations the description of the solute as a point dipole located at the centre of a cavity, the spherical fonn of the cavity and the assumption that cavity size and solute dipole moment are independent of the solvent dielectric constant. 

Kirkwood generalized the Onsager reaction field method to arbitrary charge distributions and, for a spherical cavity, obtained the Gibbs free energy of solvation in tenns of a miiltipole expansion of the electrostatic field generated by the charge distribution [12, 1 3]... 

In the reaction field method, the space surrounding a dipolar molecule is divided into two regions (i) a cavity, within which electrostatic interactions are sunnned explicitly, and (ii) a surrounding medium, which is assumed to act like a smooth continuum, and is assigned a dielectric constant e. Ideally, this quantity will be... 

When carried out properly, the results of the reaction field method and the Ewald sum are consistent [67]. Recently, the reaction field method has been reconnnended on grounds of elTiciency and ease of progrannning [68, 69]. The... 

In the reaction field method, a sphere is constructed around the molecule with a radius equal to the cutoff distance. The interaction with molecules that are within the sphere is calculated explicitly. To this is added the energy of interaction with the medium beyond the sphere, which is rnodelled as a homogeneous medium of dielectric constant g (Figure 6.23). The electrostatic field due to the surrounding dielectric is given by ... 

The reaction field method. The shaded arrow represents the mm of the dipoles of the other molecules within sphere. 

SCRF (self-consistent reaction field) method for including solvation effects in ah initio calculations... 

I. G. Tironi, R. Sperb, P. E. Smith, W. F. van Gunsteren. A generalized reaction field method for molecular dynamics simulations. J Chem Phys 702 5451, 1995. 

There is a fundamental difference between Eqs. 4.12 and 4.15 despite their apparent similarity. The term electron density (see Eq. 4.13), whereas the term Vcxt in Eq. 4.12, is constant in the SCF procedure. To reflect this fact, the approach based on Eqs. 4.13-4.15 is frequently called the Self-Consistent Reaction Field method (SCRF). (Throughout the text, AXY/SCRF denotes combined quantum-mechanical/reaction field calculations where XXX specifies the quantum-mechanical method.)... 

A. G. Angy n and G. Jensen, Are direct reaction field methods appropriate for describing dispersion interactions , Chem. Phys. Lett. 175 313 (1990). 

Inclusion of the reaction field method gives the same picture indeed, the dipole moments are simply enhanced in magnitude, but their orientation is not changed, neither in the isolated bases nor in the pairs. 

Karelson, M., Tamm, T. and Zemer, M. C. Multicavity reaction field method for the solvent effect... 

Let us now review the group of papers discussing the relative weights of the different components in Buckingham equation (Equation (2.23)). Reaction field methods describe only long-range electrostatic interaction, the crE term (or, as in IEF-PCM, some of the (rw term [29]). In order to go beyond the continuum model some solvent molecules... 

Duijnen, P.Th. van and Rullmann J.A.C., Intermodular interactions with the direct reaction field method. Int. J. Quantum Chem. (1990) 38 181-189. 

---