Well, the simplest case is when you have two identical molecules in co-facial interaction.
you will need to calculate the reorganization energies of this system and the HOMO (hole) and LUMO (electron) splitting caused by putting these two molecules together (ie, how much meV have the HOMO or the LUMO changed from the isolated molecule case to the case where you have now two of them together). you also need to know the distance that separates these two molecules. once you have all this, you should solve the Marcus mobility equation, considering that epsilon1=epsilon2 and that the DeltaG0 equals zero. This is the simplest case. if your system is consisted of different molecules, you will also have to calculate the Gibbs energies in their ionized and ground states and the total energy as well.
if your system is periodic (a crystal)... good luck!
Thank You so much Mr.Hugo Santos Silva, i will try to work by this method
A note on the method mentioned above. This only works if the molecules are symmetrically indistinguishable. If the molecules are not equivalent it does not work. and you need to calculate the electronic coupling in a different way.
Dear Hugo, excellent answer but I have one doubt i.e when we do optimization by keep two identical molecules together in a co-facial interaction as you mentioned above, those molecules will be with the same co-facial interaction (position) after optimization? If not, it effects on their mobilities?
Dear Bradley is it possible to calculate electronic coupling for different symmetry molecules using Gaussian programme?
dear Saisudhakar
considering that the two molecules are the same: you're going to do a full ground-state optimization of this isolated molecule. Once you have it, you add the same molecule in cofacial geometry and optimize it in the ionized states to obtain the reorganization energies. normally this should not translate (a lot) your molecule. it should relax within its own internal degrees of freedom. if it translates and the distance between their center of mass changes, you will have a change in the mobility value, since it depends on the inverse of squared distance between these molecules.
Dear Hugo Santos Silva, in my case i work with polymer , so is it possible that i use the same method?
If you are looking at polymers (oligomers) you very likely need to make sure you are using the correct method since the dimers are likely non-equivalent. There is a version built in to NWChem (but not well documented) and ADF. You need to have a script to take outputs and do this calculation for other programs.
See the below paper for information.
Valeev, E. F.; Coropceanu, V.; Da Silva Filho, D. A.; Salman, S.; Bredas, J.-L. Effect of Electronic Polarization on Charge-Transport Parameters in Molecular Organic Semiconductors. J. Am. Chem. Soc. 2006, 128 (30), 9882–9886.
Regarding the procedure in ADF, you can find a worked out example here:
https://www.scm.com/adf-modeling-suite/wizard/organic-electronics/electron-and-hole-mobilities-in-organic-electronics/
You can also start with your own crystal structure and cut out different dimers from a periodic (super)cell
Dear Mr. T. P M Goumans
As following the link you mentioned above, I have tried to calculate the transfer integral using the ADF program for my system, but it is showing no value in the output file.
I made the cif file of my molecule using CrytalX software (following P21/P1 space groups), then exporting the cif file to ADF and made the supercell. After that cutting the dimer from the supercell and followed the direction.But the output shows no transfer integral value. Can you please tell me what is going on?
#N:B: I tried the Naphthalene dimer example, it is working but for my molecule, it is not.
I am attaching the ADF input and output file for your kind consideration.
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