Polarization theory

Many problems in force field investigations arise from the calculation of Coulomb interactions with fixed charges, thereby neglecting possible mutual polarization. With that obvious drawback in mind, Ulrich Sternberg developed the COSMOS (Computer Simulation of Molecular Structures) force field [30], which extends a classical molecular mechanics force field by serai-empirical charge calculation based on bond polarization theory [31, 32]. This approach has the advantage that the atomic charges depend on the three-dimensional structure of the molecule. Parts of the functional form of COSMOS were taken from the PIMM force field of Lindner et al., which combines self-consistent field theory for r-orbitals ( nr-SCF) with molecular mechanics [33, 34]. 

Of particular interest is the fact that two plasticisers of similar molecular weight and solubility parameter can, when blended with polymers, lead to compounds of greatly differing properties. Many explanations have been offered of which the most widely quoted are the polar theory and the hydrogen bonding theory. 

Jphe polarization theory predicts a cross-section for collisions ... 

A central problem in studying ion-molecule reactions is the dependence of the microscopic cross-section, a or the rate constant k upon the relative velocity of the ion and the molecule. Only from reliable, established data on this dependence can one choose among the various theoretical models advanced to account for the kinetics of these processes such as the polarization theory of Gioumousis and Stevenson (10) or the more recent phase-space treatment of Light (26). 

Challenged by Thorpe ("The polarity theory explains everything and predicts nothing"), 120 Robinson made two specific predictions for substitution in nitrobenzene and chlorobenzene derivatives, which he said would be verified in his laboratory by Mr. Oxford. 121... 

The large trans labilizing ability of H is explained on the basis of the polarization theory, whereas the x-bonding theory is involked to account for the large effect of PEt8. 

Marcus calculates the outer sphere contribution to the reorganization energy from non-equilibrium dielectric continuum polarization theory for the solvent environment (— 5 nm)... 

Extremely Fast Calculation of UC Chemical Shift Tensors Using the Bond Polarization Theory... 

The semi-empirical bond polarization theory provides a fast method for the calculation of 13C chemical shift tensors with an accuracy level comparable to ab initio methods for most molecules. There are no restrictions in the size of the molecular system, so that the method can be applied to large molecules or crystal lattices. Chemical shift calculations were carried out for several small molecules and compared to ab initio results. Additionally the calculated chemical shift tensor for the fullerence Qo is presented. 

The authors of this work proposed a semi-empirical scheme for the calculation of 13C chemical shift tensors based on the bond polarization theory (5). This method can reproduce 13C chemical shift tensors with deviations from experiment comparable to the errors of the ab initio methods. One major advantage is that the calculations can be performed for large molecular systems with hundreds of atoms even on a PC computer. In contrast to the ab initio method a set of empirical parameters is needed for the calculations. In the case of the bond polarization theory these parameters can be estimated directly from experimental chemical shifts solving a set of linear equations. 

There seem to be no literature data potentially capable of showing definite consistency with Frenkel-Halsey type isotherms, with the exception of the results for nitrogen on titanium dioxide (2). Here we find that no site energy distribution can be constructed using such a local isotherm type which will lead to a fit over the entire range of data. The same appears to be true of local isotherm equations of the polarization theory type ... 

The static permittivities of mixtures of organic liquids with water may be interpreted in terms of polarization theory. We shall see that water can be used as a solvent for the determination of dipole moments of highly polar molecules, but for less polar molecules the Kirkwood-Frohlich equation has been used as a method of demonstrating molecular interactions between water and solute. 

D. W. Oxtoby. Local polarization theory for field-induced molecular multipoles. J. Chem. Phys., 72 5171-5176 (1980). 

This coal of intermediate rank has rather extensive polynuclear formation and polar functional groups. Thus we would expect dispersion, polarizability, and dipolar interactions between the substrate entities and the sorbate molecules. The polar portion of the substrate as well as the highly conjugated pi-bonded electrons most assuredly are involved in the sorption process. Such a concept is quite suggestive and compatible with the polarization theory for sorption processes (9, 13, 14), where the energetics are predicted to follow the relationship... 

G. T. Evans, Steady-state optical spin polarization. Theory of the high yield anisotropic ESR intensity, Chem. Phys. Lett. 36, 46-48 (1975). 

The bond polarization theory is a semi-empirical approach applied within the... 

---