Molecular modeling orbital surface

Anderson and Grantscharova conducted one of the first studies on the CO oxidation on Pt using a molecular orbital theory with a simple molecular model.113 They used an atom superposition and electron delocalization molecular orbital (ASED-MO) method to investigate the electrochemical oxidation of the adsorbed CO on the Pt anodes. They found that the interaction of CO(ads) with the oxidant OH(ads) was effective only at high surface coverage. 

For molecules of chemical interest it is not possible to calculate an exact many-electron wave function. As a result, we have to make certain approximations. The most commonly made approximation is the molecular orbital approximation, which is outlined in the next section. Within such a framework, it is useful to define various levels of computational method, each of which can be applied to give a unique wave function and energy for any set of nuclear positions and number of electrons. If such a model is clearly specified and if it is sufficiently simple to apply repeatedly, it can be used to generate molecular potential energy surfaces, equilibrium geometries, and other physical properties. Each such theoretical model can then be explored and the results compared in detail with experiment. If there is sufficient consistent success, some confidence can then be acquired in its predictive power. Each such level of theory therefore should be thoroughly tested and characterized before the significance of its prediction is assessed. 

Molecular orbital calculations can be used to model the location of electron density from unpaired electrons in a radical. Open the molecular models on the book s website for the methyl, ethyl, and tert-butyl radicals. The gray wire mesh surfaces in these models represent volumes enclosing electron density from unpaired electrons. What do you notice about the distribution of unpaired electron density in the ethyl radical and rert-butyl radical, as compared to the methyl radical What bearing does this have on the relative stabilities of the radicals in this series ... 

Depending on the application, models of molecular surfaces arc used to express molecular orbitals, clcaronic densities, van dor Waals radii, or other forms of display. An important definition of a molecular surface was laid down by Richards [182] with the solvent-accessible envelope. Normally the representation is a cloud of points, reticules (meshes or chicken-wire), or solid envelopes. The transparency of solid surfaces may also be indicated (Figure 2-116). 

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