Polarized continuum method

The most popular of the SCRF methods is the polarized continuum method (PCM) developed by Tomasi and coworkers. This technique uses a numerical integration over the solute charge density. There are several variations, each of which uses a nonspherical cavity. The generally good results and ability to describe the arbitrary solute make this a widely used method. Flowever, it is sensitive to the choice of a basis set. Some software implementations of this method may fail for more complex molecules. 

OPW (orthogonalized plane wave) a band-structure computation method P89 (Perdew 1986) a gradient corrected DFT method parallel computer a computer with more than one CPU Pariser-Parr-Pople (PPP) a simple semiempirical method PCM (polarized continuum method) method for including solvation effects in ah initio calculations... 

SCF (self-consistent field) procedure for solving the Hartree-Fock equations SCI-PCM (self-consistent isosurface-polarized continuum method) an ah initio solvation method... 

Thermodynamic parameters for the benzene oxide-oxepine system are calculated at MP4(SDQ)/6-31+G //HF/ 6-31G level of theory. The effect of solvent polarity on the above equilibrium is studied using the isodensity polarized continuum method. Low polar solvents favor the oxepine formation, whereas medium to high polar solvents lead to benzene oxide formation. The transition state for the tautomerization is fully characterized and the activation energies for the forward and reverse reaction are estimated to be ca. 9.5 and 11.0 kcal mol-1, respectively. The solvent polarity exerts a reasonable effect decreasing the activation energies up to 4 kcal mol-1 <2001MI471>. 

No systematic study of the effect of different solvation models has been performed. A few reports have compared specific cases such as the study of cationic and anionic alanines, which shows a significant improvement in the chemical shift prediction using polarized continuum method (PCM) or better stiU a hybrid solvation approach (Section 1.4.3). However, the linear scaling correction discussed below can often account for the systematic solvent effect and so sometimes one can get away without any solvent computation at all. 

Table 7 Lowest electronic excitation energy (in eV) and isotropic shielding constant (in ppm) <7. n gives the number of water molecules that are explicitly treated quantum theoretically. PCM denotes the standard polarized continuum method, whereas in PCM the radii spheres surrounding each atom in the construction of the cavity have been scaled by 91.7%. Finally, MM marks results obtained with an explicit description of the solvent. All results are from ref 35... 

In the second approach, an implicit solvent such as the polarized continuum method (PCM), an explicit solvent, or a combination of these methods is used in order to calculate the lithium free energy of solvation so that the conversion factor is specific for the electrolyte of interest needed for the cycle shown in Fig. 8.1b. A number of groups [7, 8] have used DFT calculations to relate the absolute and LiV Li potential scales using the thermodynamic cycles shown in Fig. 8.1a, b for the... 

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