Polarizability computation

Comparison of the interaction-induced trace and anisotropy of the Hej polarizability computed by sapt with the fci results (in 10 3 a.u.). 

P.W. Langhoff and M. Karpins, Application of Pade approximants to dispersion force and optical polarizability computations, in G.A. Baker, J.L. Gammel (Eds.), The Pade approximant in theoretical physics. Academic Press, New York, 1970, pp. 41-97. 

G. Maroulis (ed.). Atoms, Molecules and Clusters in Electric Fields. Theoretical Approaches to Calculation of Electric Polarizability. Computational, numerical and mathematical methods in science and engineering, vol. 1 (Imperial College Press, Singaprne, 2006)... 

Compounding the difficulty of accounting for electron correlation effects properly, accurate computations of noncovalent interactions also require very large basis sets. This is not surprising because London dispersion interactions can be expressed in terms of the polarizabilities of the weakly interacting molecules, and polarizability computations are known to have large basis set requirements. In many weakly bound complexes, the dispersion terms can be the dominant ones. 

Karamanis, P, Begue, D., 8c Pouchan, C. (2007a). Ab initio finite field (hyper)polarizability computations on stoichiometric gallium arsenide clusters Ga As (n = 2-9). Journal of Chemical Physics, 127(9), 094706/1-094706/10. 

Fig. 8.9. UNI lattice energies for 308 crystal structures (from the SMALL database, no hydrogen bonds) as a function of the overall molecular polarizability computed by sums of approximate atomic increments.

Periodic Table from B to Ne (and from H and He), the physical picture of bonding developed here is entirely consistent with the available information regarding atomic properties The red and green atoms which we have signaled out as supporters of CET do have large atom polarizabilities. Computational support for the concept of Overlap Dispersion has been presented in the original paper... 

Here X is tire reorganization energy associated witli the curvature of tire reactant and product free energy wells and tlieir displacement witli respect to one another. Assuming a stmctureless polarizable medium, Marcus computed the solvent or outer-sphere component of tire reorganization energy to be... 

The dielectric constant is a property of a bulk material, not an individual molecule. It arises from the polarity of molecules (static dipole moment), and the polarizability and orientation of molecules in the bulk medium. Often, it is the relative permitivity 8, that is computed rather than the dielectric constant k, which is the constant of proportionality between the vacuum permitivity so and the relative permitivity. 

Polarization is usually accounted for by computing the interaction between induced dipoles. The induced dipole is computed by multiplying the atomic polarizability by the electric field present at that nucleus. The electric field used is often only that due to the charges of the other region of the system. In a few calculations, the MM charges have been included in the orbital-based calculation itself as an interaction with point charges. 

There are several ways in which to compute polarizabilities and hyperpolari-zabilities from semiempirical or ah initio wave functions. One option is to take... 

Ah initio calculations of polymer properties are either simulations of oligomers or band-structure calculations. Properties often computed with ah initio methods are conformational energies, polarizability, hyperpolarizability, optical properties, dielectric properties, and charge distributions. Ah initio calculations are also used as a spot check to verify the accuracy of molecular mechanics methods for the polymer of interest. Such calculations are used to parameterize molecular mechanics force fields when existing methods are insulficient, which does not happen too often. 

The properties available include electrostatic charges, multipoles, polarizabilities, hyperpolarizabilities, and several population analysis schemes. Frequency correction factors can be applied automatically to computed vibrational frequencies. IR intensities may be computed along with frequency calculations. 

Polarizability Attraction. AU. matter is composed of electrical charges which move in response to (become electrically polarized in) an external field. This field can be created by the distribution and motion of charges in nearby matter. The Hamaket constant for interaction energy, A, is a measure of this polarizability. As a first approximation it may be computed from the dielectric permittivity, S, and the refractive index, n, of the material (15), where is the frequency of the principal electronic absorption... 

DE Smith, LX Dang. Computer simulations of NaCl association m polarizable water. J Chem Phys 100 3757-3766, 1994. 

More complete interpretations of Diels-Alder regioselectivity have been developed. MO results can be analyzed from an electrostatic perspective by calculating potentials at the various atoms in the diene and dienophile. These results give a more quantitatively accurate estimate of the substituent effects. Diels-Alder regioselectivity can also be accounted for in terms of HSAB theory (see Section 1.2.3). The expectation would be that the most polarizable (softest) atoms would lead to bond formation and that regioselectivity would reflect the best mateh between the diene and dienophile termini. These ideas have been applied using 3-2IG computations. The results are in agreement with the ortho rule for normal-electron-demand Diels-Alder reactions. ... 

Another way of obtaining information about the distribution of electrons is by computing the polarizability. This property depends on the second derivative of the energy with respect to an electric field. We ll examine the polarizability of formaldehyde in Chapter 4. 

The other major properties computed by a frequency job are the polarizability and hyperpolarizability tensors. Normally, the polarizability is printed at the end of the output, just before the archive entry ... 

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