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tward

Member

Registered: 2026-03-19

Posts: 1

Calculating the Exciton Couplings using TrESP

Hi,

I am trying to calculate the coupling between singlet excited states in a dimer system (the monomers are not physically bonded to each other). I am hoping that you can confirm if my interpretation of the manual is correct:

- Run excited state calculations of each monomer in Gaussian16, three singlet excited states are calculated and the state of interest is S_2.
- Calculate Tresp charges for each monomer in multiwfn and obtain two monomer_XXX.chg files
- Combine the two .chg files into one
- Run multiwfn -> dimer.chg -> 7 -> -2

Am I correct in thinking that this will give me the exciton coupling between the two S_2 states on each of the monomers (i.e.V_02,20). The value that I obtain using the above approach appears to be many orders of magnitude greater than the value that we are expecting for the exciton coupling.

Thank you in advance for your help with this

Last edited by tward (2026-03-19 12:07:05)

sobereva

Tian Lu (Multiwfn developer)

From: Athens, Greece

Registered: 2017-09-11

Posts: 2,217

Website

Re: Calculating the Exciton Couplings using TrESP

The steps are seemingly correct.

Please note that when calculating the monomers in Gaussian, "nosymm" keyword should be used to prevent Gaussian from automatically reorientating the system coordinate, otherwise the coordinates of the monomers will finally overlap with each other, and thus the calculated exciton coupling will be completely wrong.