From NWChem
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Just Got Here
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| 9:28:35 AM PST - Tue, Mar 6th 2012 |
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Hi there,
I am new to NWchem and would like to learn how to use the electron transfer module.
I read the relevant section of the manual, but it was not clear to me how to go about doing what I want to do, namely calculate the transfer integral between two sections of a conjugated molecule.
If I have understood correctly, I need to generate charge-localised vectors for the products and reactant states.
To me, the most obvious way of doing this would be to chop the molecule in two, add capping hydrogrens and optimise their neutral and charged geometries, then rebuild the entire molecule using these fragments.
If I am lucky, when I run the SCF, the charge will localise onto the part which has the relaxed charged geometry. It might be a good idea to reoptimise the whole structure, as long as the charge does not become delocalised.
However, if this does not work, I think I will have to try to force the charge to localise by superimposing fragment molecular orbitals and perhaps not running many SCF cycles following superposition. My question is how to do this if I have added hydrogens to cap my fragments? Alternatively, how to do the fragment calculations without adding hydrogens to cap the fragments?
Many thanks in advance for your help,
Mike
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Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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Forum Regular
Threads 2
Posts 286
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| 12:10:59 PM PST - Wed, Mar 7th 2012 |
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See http://www.nwchem-sw.org/index.php/Release61:Hartree-Fock_Theory_for_Molecules#Superpositi... for a description on how to do fragments. I would not use hydrogens to cap. Rather I would put an effective point charge there.
Once you have the full molecule, you can use swap as well as enforcement of the character of the orbitals, the latter only in DFT to maintain the character of the product and reactant states.
Bert
[QUOTE=Mikewykes Mar 6th 4:28 pm]Hi there,
I am new to NWchem and would like to learn how to use the electron transfer module.
I read the relevant section of the manual, but it was not clear to me how to go about doing what I want to do, namely calculate the transfer integral between two sections of a conjugated molecule.
If I have understood correctly, I need to generate charge-localised vectors for the products and reactant states.
To me, the most obvious way of doing this would be to chop the molecule in two, add capping hydrogrens and optimise their neutral and charged geometries, then rebuild the entire molecule using these fragments.
If I am lucky, when I run the SCF, the charge will localise onto the part which has the relaxed charged geometry. It might be a good idea to reoptimise the whole structure, as long as the charge does not become delocalised.
However, if this does not work, I think I will have to try to force the charge to localise by superimposing fragment molecular orbitals and perhaps not running many SCF cycles following superposition. My question is how to do this if I have added hydrogens to cap my fragments? Alternatively, how to do the fragment calculations without adding hydrogens to cap the fragments?
Many thanks in advance for your help,
Mike
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