I have modeled an oxocarbenium ion like transition state (at B3LYP/6-31+G* level of theory) with overall charge of -1. I would like to calculate and check partial charges for the molecule. So far I have used nbo analysis and it is found to be inappropriate for a highly delocalized structure like mine. I appreciate best possible approach for this kind of a molecule.
I have used q-chem code in Spartan'16 software for calculations. Possible suggestions from Gaussian is also accepted.
Regards,
D L S Dinuka
Depending on exactly what kind of analysis you want to do, you might find Bader charge analysis useful. One of its distinctive features is that it does not use any kind of orbital representation - this is an advantage if you don't have an orbital representation which accurately describes your system. I don't know if there is a script which can do Bader charges from q-chem calculations, but this one reads Gaussian output.
http://theory.cm.utexas.edu/henkelman/code/bader/
Hey Hi, have you tried ESP method for charge calculations in gaussian?
If not, try pop=esp to see if that gives you correct result.
Regards
Ajay Khanna
There are many types of atomic charges. The multiwfn program (http://sobereva.com/multiwfn) can compute most of them, such as Mulliken, SCPA, AIM (also known as Bader charge), Hirshfeld, Hirshfeld-I, ADCH, CM5, CHELPG, MK, EEM and so on. The .fch file outputted by Q-Chem can be directly used as input file.
According to my experience, the NPA charge is not necessarily inappropriate for your system; however, if you really think its result is unreliable, I highly suggest you try to compute ADCH and CHELPG charges and check if the result is more chemically meaningful.
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