Chemical population analysis

Ldwdin population analysis avoids the problem of negative populations or populations greater than 2. Some quantum chemists prefer the Ldwdin approach to that of Mulliken as the charges are often closer to chemically intuitive values and are less sensitive to basis set. 

Journal of the American Chemical Society 112 114-118. iiai ii rach S M 1994. Population Analysis and Electron Densities from Quantum Mechanics. In Lipkowitz K B and D B Boyd (Editors). Reviews in Computational Chemistry Volume 5. New York, VCl 1 Publishers, pp 171-227. 

A significant development in the FRET imaging field has been the systematic implementation of spectral resolution [15-20], including D-A population analysis [8, 19] (see also Chapter 8), often in the context of single-molecule determinations [21-26] see focus issue on this subject, Nature Methods, June 2008. Invariably, photobleaching phenomena [21, 27, 28] intervene either as a hindrance (that can be minimized, CLEM [29]) or a facilitation of the FRET determination [1, 30], The equally important issue of background suppression or compensation can be achieved by novel means photon-free (bio)chemical instead of photonic excitation... 

The first term in this expression is an entropy of mixing term related to electron transfer the second term is the information loss due to polarization of the AIM. Minimizing the information loss per atom results in the Hirshfeld population analysis [64,65] and many other results in the broad field of chemical information theory [26,66-75]. Zeroing the entropy of mixing term by choosing a reference ion that has the same number of electrons as the AIM, one obtains the Hirshfeld-I population analysis [76,77],... 

The book covers a gamut of related topics such as methods for determining atoms-in-molecuies, population analysis, electrostatic potential, molecular quantum similarity, aromaticity, and biological activity. It also discusses the role of reactivity concepts in industrial and other practical applications. Whether you are searching for new products or new research projects, this is the ultimate guide for understanding chemical reactivity. 

STANJAN The Element Potential Method for Chemical Equilibrium Analysis Implementation in the Interactive Program STANJAN, W.C. Reynolds, Thermosciences Division, Department of Mechanical Engineering, Stanford University, Stanford, CA, 1986. A computer program for IBM PC and compatibles for making chemical equilibrium calculations in an interactive environment. The equilibrium calculations use a version of the method of element potentials in which exact equations for the gas-phase mole fractions are derived in terms of Lagrange multipliers associated with the atomic constraints. The Lagrange multipliers (the element potentials ) and the total number of moles are adjusted to meet the constraints and to render the sum of mole fractions unity. If condensed phases are present, their populations also are adjusted to achieve phase equilibrium. However, the condensed-phase species need not be present in the gas-phase, and this enables the method to deal with problems in which the gas-phase mole fraction of a condensed-phase species is extremely low, as with the formation of carbon particulates. 

Natural population analysis was carried out on 273 and 282. As shown in Figure 1, the positive charge of both cations is localized on the carbon atoms of the three-membered ring. This is consistent with the conclusion, based on C chemical shifts of benzocyclopropenyl cations, that about 45% of the positive charge resides in the cyclopropene moiety. ... 

This localization scheme permits tire assignment of hybridization both to the atomic lone pairs and to each atom s contributions to its bond orbitals. Hybridization is a widely employed and generally useful chemical concept even though it has no formal basis in the absence of high-syrnmetry constraints. Witli NBO analysis, tire percent s and p character (and d, f, etc.) is immediately evident from tire coefficients of tire AO basis functions from which the NAO or NBO is formed. In addition, population analysis can be carried out using the NBOs to derive partial atomic charges (NPA, see Section 9.1.3.2). 

NICS NPA nucleus-independent chemical shift natural population analysis... 

Chemical bonds and population analysis Most metals of interest in the context of polymer-based electronic devices form some kind of chemical bond to the polymer upon interaction with a polymer surface. Population analysis, based on the electronic structure, is used to determine the character of this bond. According to the commonly used chemical terminology, bonds are classified as ionic if the bonded atoms are oppositely charged and held together by the attractive Coulomb force, and covalent if the two atoms are neutral but share the same pair of electrons. In the latter case, much of the electron density is located between the bonded atoms whereas for the ionic bond the charge density is concentrated at the atomic sites. 

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