Hi, there is an alternative quite useful. If you have used Gaussian, you can obtain the wavefunction (file.wfn) and the checkpoint (file.chk)

Obtain the fchk file (using gaussian tools) and after that the cube file (cubegen tool) for the MEP. (POT keyword)

Then you can plot the MEP over any isosurface with WFA (using wfn and cub files). 

I hope this helps you

Cheers

Goar

Dear Dr. Goar Sanchez,

Thank you very much for your help. I followed your instruction and it nicely worked. Also, I have found WFA does not have any problem with dummy and ghost atoms, my initial wfn was the problem.

Best wishes,

Sirous