Conductor-like Screening Model

When the Poisson equation is solved using a boundary element approach, the charges on the tesselated molecular surface are determined so that they provide an equivalent representation 

Of course, the response of a conductor to a solute charge distribution is complete , while that of a dielectric medium is not. So, in COSMO models, the more simply evaluated conductor-polarization free energy is scaled by a factor of 2(s — l)/(2e -f-1) after its computation (i.e., by the Onsager factor in the case of the SM5C model, however, the scaling factor is (e — l)/e - see Section 11.3.3). 

Since its original description at the semiempirical level, COSMO has also been generalized to the ab initio and density functional levels of theory as well (Klamt et al. 1998). In addition, conductor-like modifications of the PCM formalism have also been described, and to distinguish between the conductor-like version and the original (dielectric) version, the acronyms C-PCM and D-PCM have been adopted for the two, respectively (Barone and Cossi 1998). 

From a chemical perspective, dielectric- and conductor-like continuum models give sufficiently similar electrostatic results that the differences in their underlying assumptions appear to have no impact. Conductor-like models seem to be slightly more computationally robust in some instances, which may make tliem a better choice if instability is manifest in an SCRF calculation. Some concerns were raised initially that the post facto correction for dielectric behavior might render the models appropriate only for media having reasonably high dielectric constants, but a systematic study by Dolney et al. (2000) indicated non-polar solvents to be equally amenable to treatment by a COSMO model. 

It is important to re-emphasize that the electrostatic component of the solvation free energy is not a physical observable. Thus, it is impossible to assert on any basis other 

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Klamt A 1995. Conductor-like Screening Model for Real Solvent A New Approach to the Quantitativt Calculation of Solvation Phenomena. Journal of Physical Chemistry 99 2224-2235. 

The conductor-like screening model (COSMO) is a continuum method designed to be fast and robust. This method uses a simpler, more approximate equation for the electrostatic interaction between the solvent and solute. Line the SMx methods, it is based on a solvent accessible surface. Because of this, COSMO calculations require less CPU time than PCM calculations and are less likely to fail to converge. COSMO can be used with a variety of semiempirical, ah initio, and DFT methods. There is also some loss of accuracy as a result of this approximation. 

COSMO (conductor-like screening model) a method for including solvation effects in orbital-based calculations... 

COSMO-RS conductor-like screening model for realistic solvation... 

In 1995, one of the authors (A.K.) introduced the state of a molecule embedded in a perfect conductor as an alternative reference state, which is almost as clean and simple as the vacuum state. In this state the conductor screens all long-range Coulomb interactions by polarization charges on the molecular interaction surface. Thus, we have a different reference state of noninteracting molecules. This state may be considered as the North Pole of our globe. Due to its computational accessibility by quantum chemical calculations combined with the conductor-like screening model (COSMO) [21] we will denote this as the COSMO state. 

Klamt, A. Conductor-like screening model for real solvents a new approach to the quantitative calculation of solvation phenomena. J. Phys. Chem. 1995, 99, 2224-2235. 

D. M. Dolney, G. D. Hawkins, P. Winget, D. A. Liotard, C. J. Cramer, and D. G. Truhlar, A universal solvation model based on the conductor-like screening model, J. Comput. Chem. 21 340 (2000). 

In addition to these external electric or magnetic field as a perturbation parameter, solvents can be another option. Solvents having different dielectric constants would mimic different field strengths. In the recent past, several solvent models have been used to understand the reactivity of chemical species [55,56]. The well-acclaimed review article on solvent effects can be exploited in this regard [57]. Different solvent models such as conductor-like screening model (COSMO), polarizable continuum model (PCM), effective fragment potential (EFP) model with mostly water as a solvent have been used in the above studies. 

Conductor-like screening model (COSMO) is one of variants of PCM method [29]. In this method, the cavity is considered to be embedded in a conductor with an infinite dielectric constant [29]. An extension to this method, called COSMO-RS... 

Conductor-like screening model for real solvenfs COSMO-RS... 

Here, r denotes the position vector of the charges qt with respect to the center of the sphere, and r, the distance from the center. By applying the dielectric scaling function for dipoles (Eq. (2.3)), which—as we have seen in Fig. 2.1—is also a good approximation for most other multipole orders, it was immediately clear that the idea of using a scaled conductor instead of the EDBC leads to a considerable simplification of the mathematics of dielectric continuum solvation models, with very small loss of accuracy. It may also help the finding of closed analytic solutions where at present only multipole expansions are available, as in the case of the spherical cavity. Thus the Conductor-like Screening Model (COSMO) was bom. 

In addition to SMx and the cluster-continuum model, other continuum models have also been used to study reactions in liquids, including the polarized continuum model [133-135] (PCM), the conductor-like screening model (COSMO [136] and COSMO-RS [137,138]), the generalized COSMO [139] (GCOSMO) model, conductorlike PCM [140] (CPCM), and isodensity PCM [141] (IPCM). 

Fig. 9 Nuclear spin-spin coupling constants J(195Pt-205Tl) for complexes I-V (see Fig. 8), from ZORA DFT computations. Data taken from Autschbach and Le Guennic [126]. Different computational models were applied Model A includes explicit water molecules. In Model B, a continuum model (conductor-like screening model, COSMO) is applied in addition to the explicit solvent molecules of model A. Model C differs from model B in that instead of the VWN functional the statistical averaging of orbital potentials (SAOP) XC potential was used, which allows more accurate computations of NMR parameters [32]. The NMR measurements were carried out in aqueous solution [99,130]...

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