Connectivity-polarizability

The Hine and Mookerjee method has lasted well but is now outdated, and the similar Meylan and Howard correlation supercedes it. This method has the significant advantage of transparency and simplicity thus it is preferred by many over the more complex and less intuitively satisfying connectivity/polarizability methods. If time is available, and espe-... 

Three major approaches to the prediction of aqueous solubility of organic chemicals using Quantitative Structure Activity Relationship (QSAR) techniques arc reviewed. The rationale behind six QSAR models derived from these three approaches, and the quality of their fit to the experimental data are summarized. Their utility and predictive ability are examined and compared on a common basis. Three of the models employed octanol-water partition coefficient as the primary descriptor, while two others used the solvatochromic parameters. The sixth model utilized a combination of connectivity indexes and a modified polarizability parameter. Considering the case of usage, predictive ability, and the range of applicability, the model derived from the connectivity- polarizability approach appears to have greater utility value. 

To display properties on molecular surfaces, two different approaches are applied. One method assigns color codes to each grid point of the surface. The grid points are connected to lines chicken-wire) or to surfaces (solid sphere) and then the color values are interpolated onto a color gradient [200]. The second method projects colored textures onto the surface [202, 203] and is mostly used to display such properties as electrostatic potentials, polarizability, hydrophobidty, and spin density. 

This result, called the Clausius-Mosotti equation, gives the relationship between the relative dielectric constant of a substance and its polarizability, and thus enables us to express the latter in terms of measurable quantities. The following additional comments will connect these ideas with the electric field associated with electromagnetic radiation ... 

The connection between the molar polarization Pm and the molar refraction Rm is through Maxwell s theory of electromagnetism, according to which e = (at low-frequency fields). This is the basis for considering the molar refraction a measure of polarizability. 

Kier and coworkers found that the molecular connectivity-index and such molecular properties as polarizability, molecular volume," and partition coefficients between water and octanol"" show very good correlation. Because all of these properties could be correlated with biological activity. 

To summarize, if the low-lying states connected to the ground state by allowed dipole transition are not valence states but present a predominant Rydberg character, we have to introduce a lot of n) states if not, the value of dynamic polarizability near the first resonance is poor. 

The development of the methods described in Section 9.2 was an important step in modeling polarization because it led to accurate calculations of molecular polarizability tensors. The most serious issue with those methods is known as the polarization catastrophe since they are unable to reproduce the substantial decrease of the total dipole moment at distances close to contact as obtained from ab initio calculations. As noted by Applequist et al. [49], and Thole [50], a property of the unmodified point dipole is that it may originate infinite polarization by the cooperative interaction of the two induced dipoles in the direction of the line connecting the two. The mathematical origins of such singularities are made more evident by considering a simple system consisting of two atoms (A and B) with isotropic polarizabilities, aA and c b. The molecular polarizability, has two components, one parallel and one perpendicular to the bond axis between A and B,... 

It is also worth noting that Equation 9.1 indicates a connection between C44, hardness, and e. The dielectric constant, e depends on the polarizability, a of each alkali halide through the Clausius-Mossotti equation ... 

The connection between hardness and a measure of the ease with which a crystal can change its shape is its reciprocal polarizability (as shown above). The softer the crystal, the greater its polarizability. The hardnesses have the dimensions of pressure, and the polarizabilities are derived from the dielectric constants through the Clausius-Mosottii equation. That is ... 

An implication of the connection with polarizability is that structural transformations may occur when the external work done is just enough to equal Eg (AVIV). That is, just enough to close the band-gap. This suggestion was originally made by Jamieson (1963), and was supported by studies of Gilman (1993). 

Balaban-type index from polarizability weighted distance matrix connectivity index chi-0... 

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