Politz

J.S. Munay, P. Politzer, Electrostatic potential, in Encyclopedia of Gjmpu-tational Chemistry, Vol.2, P. von Rague-Schleyer, N.L. Allinger, T. Clark, J. Gasteiger, P.A. Kollman, H.F. Schaefer III, P.R. Schreiner (Eds.) John Wiley Sons, Chichester. UK, 1998, pp. 912-920. 

The MEP at the molecular surface has been used for many QSAR and QSPR applications. Quantum mechanically calculated MEPs are more detailed and accurate at the important areas of the surface than those derived from net atomic charges and are therefore usually preferable [Ij. However, any of the techniques based on MEPs calculated from net atomic charges can be used for full quantum mechanical calculations, and vice versa. The best-known descriptors based on the statistics of the MEP at the molecular surface are those introduced by Murray and Politzer [44]. These were originally formulated for DFT calculations using an isodensity surface. They have also been used very extensively with semi-empirical MO techniques and solvent-accessible surfaces [1, 2]. The charged polar surface area (CPSA) descriptors proposed by Stanton and Jurs [45] are also based on charges derived from semi-empirical MO calculations. 

In the Lowdin approach to population analysis [Ldwdin 1970 Cusachs and Politzer 1968] the atomic orbitals are transformed to an orthogonal set, along with the molecular orbital coefficients. The transformed orbitals in the orthogonal set are given by ... 

Modern Density Functional Theory J. M. Seminario, P. Politzer, Eds., Elsevier, Amsterdam (1995). 

M. P. Allen, D. J. Tildesley, Computer Simulation of Liquids Oxford, Oxford (1987). Chemical Applications of Atomic and Molecular Electrostatic Potentials P. Politzer, D. G. Truhlar, Eds., Plenum, New York (1981). 

J. S. Murray, P. Politzer, Theoretical Orqanic Chemistry C. Parkanyi, Ed., 189, Elsevier, Amsterdam (1998). 

POLITZER, Anomalous properties of fluorine, J. Am. Chem. Soc. 91, 6235-7 (1969) Some anomalous properties of oxygen and nitrogen, Inorg. Chem. 16, 3350-1 (1977). 

Politzer, P. Weinstein, H. Some Relations Between Electronic Distribution and Electronegativity J. Chem. Phys. 1979, 71, 4218-4220. 

Grenier JC, Pouchard M, Hagenmuller P (1981) Vacancy Ordering in Oxygen-Deficient Perovskite-Related Ferrites. 47 1-25 Grice ME, see Politzer P (1993) 80 101-114... 

Politzer P, Murray JS, Grice ME (1993) Charge Capacities and Shell Structures of Atoms. 80 101-114... 

Murray,). S., Politzer, P. Relationships between solute hydrogen-bond acidity/ basicity and the calculated electrostatic potential./. Chem. Res. (S) 1992,... 

P. Politzer and J. S. Murray (eds.). Quantitative Treatments of Solute j Solvent Interactions, Elsevier, Amsterdam, 1994. 

Johnson, B. G., 1995, Development, Implementation and Applications of Efficient Methodologies for Density Functional Calculations in Modem Density Functional Theory -A Tool for Chemistry, Seminario, J. M., Politzer, P. (eds.), Elsevier, Amsterdam. 

The Lewis dot formalism shows any halogen in a molecule surrounded by three electron lone pairs. An unfortunate consequence of this perspective is that it is natural to assume that these electrons are equivalent and symmetrically distributed (i.e., that the iodine is sp3 hybridized). Even simple quantum mechanical calculations, however, show that this is not the case [148]. Consider the diiodine molecule in the gas phase (Fig. 3). There is a region directly opposite the I-I sigma bond where the nucleus is poorly shielded by the atoms electron cloud. Allen described this as polar flattening , where the effective atomic radius is shorter at this point than it is perpendicular to the I-I bond [149]. Politzer and coworkers simply call it a sigma hole [150,151]. This area of positive electrostatic potential also coincides with the LUMO of the molecule (Fig. 4). 

Politzer, P. and Murray, J.S. (1990) Chemical applications of molecular electrostatic potentials, Transactions ACA, 26, 23-39. 

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