Oscail Tutorials

Plotting electrostatic potential coloured molecular surface map
 
This plot can be obtained for any molecule or ion optimized using Orca. The first example used here is
the Zwitterion NH₃C₆H₄CO₂ which was built in Moilin and ClF₃ is described below.

 

Click the MultiWFN button and select the ESP calculation

Click OK.

When the calculation has finished the message

appears. The VMD files are copied from the current folder to c:\moilin\scratch. Start VMD

and type the commands cd c:/moilin/scratch and source esp.vmd. N.B. These commands are case sensitive and cd uses the Unix style forward slash /.

The picture should appear.

The positive end is RED and the negative end is BLUE.

CLF₃ electrostatic potential isosurface compared to Mulliken and Hirshfeld Charges

In Moilin build and optimize ClF3 using Orca.and calculate the ElectroStatic Potential surface as above.

This is not what might be expected. The F on the right does not appear to have much negative charge.

If you look at the default atom charges by checking Atom Labels and Atom Charge Labels in Setup.

The F on the right has a significant negative charge of -0.283. However these are Mulliken charges.
Mulliken charges are calculated in Hilbert space whereas the Electrostatic surface potential is calculated in real space. For more details see DOI:10.1002/qua
If you calculate Hirschfeld charges (sixth option on the MultiWFN dialog) you get

This is much closer to the ElectroStatic Potential surface calculated for ClF₃.
If you calculate the ELFTopmod type calculation then the disposition of electrons about the Cl still determines the molecular geometry.