Electronegativity equalization scheme

All these findings could ultimately lead to the construction of a non-parametrized electronegativity equalization scheme, permitting the calculation... 

T values can be tabulated as a function of the distance and the environment and incorporated in a database. Inclusion of these parameters in electronegativity equalization schemes could indeed seriously decrease the degree of empiricism present. 

One solution to the above difficulties that has been applied to ionic materials is to use a variable charge potential model. Here the charges are usually determined according to an electronegativity equalization scheme, wherein the energy of an ion is expanded as... 

De Proft F, Langenacker W, Geerhngs P (1995) A non-empirical electronegativity equalization scheme. Theory and apphcations using isolated atom properties. J Mol Struct Theochem 339 45-55... 

Bultinck, P., Langenaeker, W., Lahorte, P., de Proft, R, Geerlings, P., van Alsenoy, C., and Tollenaere, J.P., The electronegativity equalization method. I. Applicability of different atomic charge schemes, J. Phys. Chem. A, 106, 7895-7901, 2002b. 

The dipole polarizability model is not the only way in which polarization effects can be included in an MM force field. An alternative, although less widely used, scheme is based upon the concept of electronegativity equalization [38, 39]. In the most common version of the method it is supposed that the electrostatic energy of a MM system, Ee ec, can be written as ... 

Bultinck P, Langenaeker W, Lahorte P, De Proft F, Geerlings P, Van Alsenoy C, Tollenaere JP (2002) The electronegativity equalization method ii applicability of different atomic charge schemes. J Phys Chem A 106(34) 7895-7901... 

An example of quantum mechanical schemes is the oldest and most widely used Mulliken population analysis [1], which simply divides the part of the electron density localized between two atoms, the overlap population that identifies a bond, equally between the two atoms of a bond. Alternatively, empirical methods to allocate atomic charges to directly bonded atoms in a reasonable way use appropriate rules which combine the atomic electronegativities with experimental structural information on the bonds linking the atoms of interest. A widely used approach included in many programs is the Gasteiger-Hiickel scheme [1]. 

The discovery that tert-butylfluoroacetylene oligomerised spontaneously (ref. 1) could be explained by ground state destabilisation resulting from combining electronegative sp-carbon with fluorine. The "Electronegativity Effect" (ref. 2) produces maximal thermodynamic stability for substituents on carbon with complementary polarity, whereas equal polarity generally leads to destabilisation (Scheme 1, ref. 3). 

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