Effective charges of atoms

Using Slater s rules for the estimation of the effective charges of atoms (Z ), but taking into account screening by all the electrons of the atom, which increases the Z values by 0.35 as compared with Slater s, Allred and Rochow obtained the following expression for the calculation of X ... 

Taking into account the interaction of effective charges of atoms, the total energetic polarizing effect is... 

The effective charges of atoms in crystals, rather than molecules, can be determined by Szigeti s spectroscopic method [55], which is also described in details in Chap. 11, using the formula... 

Effective charges of atoms are known only for a small minority of polar molecules and crystals, therefore it is important to find a dependence of these values on such characteristics of atoms which allows to estimate the polarity of bonds a priori. Such characteristic is the electronegativity of atom (EN) which, according to Pauling who introduced this concept in 1932, is the measure of the power of an atom in a molecule to attract electrons. 

Barinsldi RL (1960) Determination of the effective charges of atoms in complexes from the X-ray absorption spectra. J Struct Chem 1 183-190... 

Batsanov SS, Ovsyannikova lA (1966). X-ray spectroscopy and effective charges of atoms in compounds of Mn. In Chemical bond in semiconductors thermodynamics. Nauka, Minsk... 

Batsanov SS (1971) Electronegativity and effective charges of atoms. Znanie, Moscow (in... 

Batsanov SS (1977) Calculation of the effective charges of atoms in solid solutions. Russ J Inorg Chem 22 941-943... 

What is the source of delocalized electrons in a compressed MX In an ionic compound, M+X, it is the anion, because A(X) < 7(M+) in a covalent compound, MX, it is the metal since 7(M) < 7(X). This question may be solved experimentally, using X-ray and/or electron spectroscopy under pressure. There are indications that the effective charges of atoms in MX compounds change under pressure in some cases the bond ionicities increase, in others decrease with the increase of pressure (see Sect. 2.6). 

Despite the qualitative validity of such comparisons, the precise relation between polarization and the electronic structure of a substance has been found only within the spectroscopic approach, which has permitted to determine separately the atomic Pa) and electronic (P ) polarization and also the effective charges of atoms by measuring the intensities of infrared (IR) absorption bands in molecules. Evidently, the ratio Pa/Patomic charges are also approximate owing to the neglect of anharmonism and changes in the orbital overlaps during vibrations of atoms. 

Table 1. The valence, averaged number of valence electrons net charges and effective charges of atoms q% in the (Gao.9325Mno,o40625Mni.oo9375A-So.oi75)As alloy.

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