Potential model, charge

However, with the improved resolution of modem XPS instruments, BE shifts as small as 0.1 eV can be detected and may be significant. These shifts can be interpreted, to a first approximation, by changes in the atomic charge (an intraatomic effect), but to account for more subtle differences, as seen in the mixed-metal phosphides M aM P and mixed arsenide phosphides MAsi -VP>, the role of next-nearest neighbours cannot be neglected. These interatomic effects, as incorporated into the charge potential model, help explain the unusual trends in BE observed in these series. 

Fig. 21. Theoretically calculated and experimentally determined Cls core binding energies for 50/50 alternating copolymer of ethylene and tetrafluoroethylene. Also shown are charge distributions obtained by direct SCF computation and from the experimental binding energies by inversion of the charge potential model...

Fig. 28. Conformational models of polyacrylic acid with calculated binding energies from the charge potential model shown for (a) HT-HT isotactic model, (b) HT-HT syndiotactic model, (c) HH-HT isotactic model and (d) HH-HT syndiotactic model (HH head to head, HT head to tail)...

By using the XPS chemical shifts and the charge potential model of Siegbahn et al (1 ) to calculate the net charge distribution, as described previously, we verify that the N atom is the primary reaction site for the PIM adsorbate (12). 

The charge-potential model was used to predict the chemical shifts for functional groups in a number of model compounds containing primarily carbon, fluorine, and hydrogen. The molecular structure examined included aliphatics, olefins, aromatics, and several ketones. 

Figure 1. Charge-potential model correlation for determination of and b...

Our third approximation, C, describes in the point-charge-potential model. Again, El depends solely on the charges found outside the core region k. but in the field of an expanded effective nuclear charge , Zl — Zi — Nl-... 

Dynamics Study of Water from Ambient to Sub- and Supercritical Conditions Using a Fluctuating-Charge Potential Model. 

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... 

Although classical models, such as the charge potential model and the equivalent-core approximation, have been developed to account for the ehemical shift [29], determination of the chemical state is more frequently practiced by comparing the experimentally measmed E with those in databases and well-defined references after carefnlly removing the charging effect. When the E variation is too small to claim a reliable chemical shift, for example, the Cn 2pg BEs of Cu O and metallic Cu are nearly identical, and the BE difference of Ag Sd between Ag O... 

The charge-potential model is a simple model that relates the core level BE to atomic charge ... 

The central role of the charge potential model in quantifying experimental data on complex molecules is shown in Fig. 28. 

Fig. 27. Values of k In the charge potential model for the Cis levels of series of organic compounds.

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