Electronegativity model

Electronegativity Model for Barrier Formation at Metal/Organic... 

The electronegativity model has been used successfully on metal/organic semiconductor interfaces, and shown to give a satisfactory description of the interface barrier formation. As electronegativity is defined only for elements it is of interest to investigate if the electronegativity model can be extended to compound electrodes such as indium tin oxide (ITO), which... 

Nau WM (1997) An electronegativity model for polar ground-state effects on bond dissociation energies. J Phys Oigan Chem 10 445-455... 

Schmidt, PC., B6hm, M. C. (1983). Atomic and molecular orbital electronegativity models based on the transition state and transition operator approaches. Ber. Bunsenges. Phys. Chem. 87,925-932. 

This model (e.g., implemented in MMFF) allows the charges on each atom i to be modified by the electronegativity of the bonded atoms j. The additional charge q is normally zero, but it ensures that the correct total charge of a molecule or fragment is maintained. 

A guide to tire stabilities of inter-metallic compounds can be obtained from the semi-empirical model of Miedema et al. (loc. cit.), in which the heat of interaction between two elements is determined by a contribution arising from the difference in work functions, A0, of tire elements, which leads to an exothermic contribution, and tire difference in the electron concentration at tire periphery of the atoms, A w, which leads to an endothermic contribution. The latter term is referred to in metal physics as the concentration of electrons at the periphery of the Wigner-Seitz cell which contains the nucleus and elecUonic structure of each metal atom within the atomic volume in the metallic state. This term is also closely related to tire bulk modulus of each element. The work function difference is very similar to the electronegativity difference. The equation which is used in tire Miedema treatment to... 

How does the Hiickel ff-electron model deal with pyridine Nitrogen is more electronegative than carbon, so the N atom ought to have a higher (more negative) T-electron charge than a carbon atom in benzene. It is conventional to write the heteroatom (X and Y are used to denote heteroatoms such as N and O) parameters in terms of the standard ac and yScc... 

Another type of correction, which is related to cross terms, is the modification of parameters based on atoms not directly involved in the interaction described by the parameter. Carbon-carbon bond lengths, for example, become shorter if there are electronegative atoms present at either end. Such electronegativity effects may be modelled by adding a correction to the natural bond length based on the atoms which are attached to the A-B bond. 

Every alternating atom in the PDMS chain is the electronegative oxygen, which makes it a polar polymer. The authors observed that at low loadings of PDMS, PVC is destabilized. This is to be expected according to the alternative model for degradation and stabilization of PVC put forward by Naqvi. But for compositions with 50% or more PDMS, both polymers are stabilized. No possible explanation can be given for this reversal in thermal stability at this time. 

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