WebMO Support Forum

How does WebMO calculate EFD?
It would seem that a Fukui f- function grid is calculated (and stored as f-.cub), then this is mapped onto a total electron density surface (stored as density.cub). E.g. in Jmol this might look like: "isosurface EFD cutoff 0.002 density.cub color absolute 0.000 0.0005 map f-.cub".
I am using Tian Lu's Multiwfn program to try and understand WebMO's surface generation theory and method. In Multiwfn, I generate the two .cub files, then display the mapped surface with the above Jmol command. However, the resulting surface, while vaguely similar, is significantly different from WebMO's. Multiwfn has almost every known kind of wavefunction calculation, so this should be possible.

Electrophilic...

BTW, I am using Gaussian to optimize the molecule and carry out a Molecular orbital calculation in WebMO. And Multiwfn is also using Gaussian to calculate f- and density .cub's at the same level of theory.

If memory serves, the Fukui density should be similar to the WebMO "radical" frontier density. This includes contributes from both HOMO and LUMO, which in the Fukui surface is Boltzmann-weighted depending on energy.

The Electrophilic (HOMO) density is similar, but contains only contributions from the occupied orbital and not the virtual ones.

Thanks J.R.,
Yes its apparent that WebMO uses the orbital-weighted Fukui function. When the delta value is set at 0.08 in Multiwfn, the weightings of HOMO, HOMO-1, and HOMO-2 are 99.5%, 0.5%, and 0.0%. With these values the WebMO electrophilic frontier density surface can be reproduced using Multiwfn and Jmol. The point of this exercise was to reverse engineer the EFD display given the absence of a detailed description in WebMO documentation.
For details see the attached PDF.