Charge distribution applications

Feil, D. (1991) X-ray diffraction and charge distribution application to the electron density distribution in the hydrogen bond, In TheApplication of Charge Density Research to Chemistry and Drug Design, Jeffrey, G.A. and Piniella, J.F. (Eds.), NATO ASI Series B250, Plenum Press, New York. 

D. T. Edmonds, N. K. Rogers, and M. J. E. Sternberg, Mol. Phys., 52, 1487 (1984). Regular Representation of Irregular Charge Distributions. Application to Electrostatic Potentials of Globular Proteins. 

This coding is performed in three steps (cf Chapter 8) First the 3D coordinates of the atoms arc calculated using the structure generator CORINA (COoRdlNAtes). Subsequently the program PETRA (Parameter Estimation for the Treatment of Reactivity Applications) is applied for calculating physicochemical properties such as charge distribution and polarizability. The 3D information and the physicochemical atomic properties are then used to code the molecule. 

However, unlike point charges, the continuous charge distributions that occur in quantum chemistry have varying extents and the applicability of the multipole approximation is not only limited by the distance but also by the extent or diffuseness of the charge distribution. This additional complexity makes a transfer of the concepts of the fast multipole method to applications in quantum chemistry less straightforward. Therefore it should come as no surprise that several adaptations to extend the applicability of the FMM to the Coulomb problem with continuous charge distributions have been suggested. These lead to... 

Geerhngs, P., De Proft, F., Martin, J. M. L., 1996, Density Functional Theory Concepts and Techniques for Studying Molecular Charge Distributions and Related Properties , in Recent Developments and Applications of Modem Density Functional, Seminario, J. M. (ed.), Elsevier, Amsterdam. 

Cong Y, Yang ZZ (2000) General atom-bond electronegativity equalization method and its application in prediction of charge distributions in polypeptide. Chem Phys Lett 316(3-4) 324-329... 

In the 1920s it was found that electrons do not behave like macroscopic objects that are governed by Newton s laws of motion rather, they obey the laws of quantum mechanics. The application of these laws to atoms and molecules gave rise to orbital-based models of chemical bonding. In Chapter 3 we discuss some of the basic ideas of quantum mechanics, particularly the Pauli principle, the Heisenberg uncertainty principle, and the concept of electronic charge distribution, and we give a brief review of orbital-based models and modem ab initio calculations based on them. 

In this review, we present a selection of studies from our own laboratory, intended to introduce a solid-state chemist to both the practical and theoretical considerations that need to be taken into account in XPS measurements of solids with substantial covalent character. Metal phosphides, arsenides, and antimonides represent such a category of solids where the bonding retains some polarity that notions of electron counting derived from the Zintl concept still prove helpful in providing a frame of reference for comparing charge distributions. We also describe the applications of XAS to complementary studies of the electronic structure of these materials. 

This may find application in biological and other systems. One way in which the effective thermodynamic barrier can be modified is through the movement of a charged group near one of the reactants since the charge distribution following electron... 

If micellar charge effects can be related to charge distribution in the transition state, as we suggest, they should be applicable to the elucidation of mechanisms of spontaneous hydrolyses, and we illustrate this approach by... 

These definitions apply to any atomic system, molecule or crystal. Fig. 7.3 a illustrates their application to the charge distribution of the guanine-cytosine base-pair. Fig. 7.3 b shows the molecular structure defined by the bond paths and the associated CPs that clearly and uniquely define the three hydrogen bonds that link the two bases. Fig. 7.3 c shows the atomic boundaries and bond paths overlaid on the electron density in the plane of the nuclei. All properties of the atoms can be determined, enabling one, for example, to determine separately the energy of formation of each of the three hydrogen bonds. 

Charge density-NMR chemical shift correlation in organic ions, 11, 125 Charge distribution and charge separation in radical rearrangement reactions, 38, 111 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminesance of organic compounds, 18, 187 Chiral clusters in the gas phase, 39, 147... 

Another arena for the application of stochastic frictional approaches is the influence of ionic atmosphere relaxation on the rates of reactions in electrolyte solutions [19], To gain perspective on this, we first recall the early and often quoted triumph of TST for the prediction of salt effects, in connection with Debye-Hiickel theory, for reaction rates In kTST varies linearly with the square root of the solution ionic strength I, with a sign depending on whether the charge distribution of the transition state is stabilized or destabilized by the ionic atmosphere compared to the reactants. 

Charge Distribution, Inductive and Resonance Effects. Until now, the discussion has been concerned with models based on additivity schemes and their modifications. However, we have also explored other types of models that can be put into algorithms that are fast, albeit less convenient for pencil and paper application. 

Seiler and Dunitz point out that the main reason for the widespread acceptance of the simple ionic model in chemistry and solid-state physics is its ease of application and its remarkable success in calculating cohesive energies of many types of crystals (see chapter 9). They conclude that the fact that it is easier to calculate many properties of solids with integral charges than with atomic charge distributions makes the ionic model more convenient, but it does not necessarily make it correct. 

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