Elpot surface

Chemists also need to know the distribution of electric charge in a molecule, because that distribution affects its physical and chemical properties. To do so, they sometimes use an electrostatic potential surface (an elpot surface), in which the net electric potential is calculated at each point of the density isosurface and depicted by different colors, as in Fig. C.2f. A blue tint at a point indicates that the positive potential at that point due to the positively charged nuclei outweighs the negative potential due to the negatively charged electrons a red tint indicates the opposite. 

Part Two. Using the density-elpot surface plot described in Experiment 20D, it is possible to compare the amount of charge delocalization in various carbocations through a visualization of the ions. Complete Experiment 20D, and determine whether the charge distributions (delocalization) are what you would expect for the series of carbocations studied. 

It is also possible to map a calculated property onto an electron-density surface. Because all three Cartesian coordinates are used to define the points on the surface, the property must be mapped in color, with the colors of the spectrum red-orange-yellow-green-blue representing a range of values. In effect, this is a four-dimensional plot (x, y, z, -i- property mapped). One of the most common plots of this type is the density-electrostatic potential, or density-elpot, plot. The electrostatic potential is determined by placing a unit positive charge at each point... 

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