Electrostatic Interactions -- Electron Density and Electrostatic Potential

Task: Generate and visualize the electron density surface colored by electrostatic potential for nitrocyclopentadiene  (). 

Time: 3 minutes

The electron density surface colored by electrostatic potential shows the charge distribution in a molecule. 

1. Open the file if necessary (File|Open "nitrocyclo-PM5")
2. Select Experiment|New.
3. Select:
1. Property of: Chemical Sample
2. Property: electrostatic potential on electron density
3. Using: PM5 geometry with PM5 wavefunction
4. Click Start.
4. The calculation window opens.  Information about the progress of the experiment scrolls in the window.  When the calculation is done, it will say "Tabulation complete".
5. Save the molecule: File|Save "nitrocyclo-PM5"
6. Visualize the surface:
   1. Select Analyze|Show Surfaces.   A Show Surfaces dialog box opens containing a list of Displayed surfaces.
   2. Locate the surface with the name nitrocyclo-PM5.csf.EonD. The file names for other surfaces may be listed as well.  A check mark will appear when you click on the name nitrocyclo-PM5.csf.EonD. 
   3. Click OK.  Your molecule displays a surface colored to reflect the magnitude and polarity of the electrostatic potential. 
7. Initially, the surface will be transparent; you can see the molecule "inside" the surface.  Clicking anywhere in the Workspace (no bonds or atoms) selects the surface.
8. To see what the different colors mean, select Analyze|Surface Legend.  A color legend appears.  The negative numbers represent areas of negative electrostatic potential (the nitro region in this case), the positive numbers represent regions of positive electrostatic potential (the cyclopentadiene ring).

In the next lesson, you will generate and visualize the Electrophilic Susceptibility surface of nitrocyclopentadiene.