Dear researchers,
I calculated the Mulliken and Hirshfield charge using CASTEP and DMol3.
However, I have no clue on how to calculate the data given from the .outmol and castep.
how to calculate the charge transfer using the data given. Thank you in advance.
I'm not quite sure what you're asking. Do you want to know how these charges are computed, or are you interested in analysing these charges and seeing what they mean? If it's the latter, then I see from your screenshots that the atoms are almost entirely neutral, so there is essentially no charge transfer. Is that what you expect?
Yes i want to analyse the charge. Do i need to sum all the atoms's charge to get the total charge? And how to calculate the total charge? @philip james hasnip
Yes, summing the charges up for all the atoms in a fragment will give you the total charge of that fragment. For example, if you had a simulation of a molecule adsorbed on a surface, you could add up all the charges of the atoms in the molecule to get the total charge on the molecule.
If you add the charges for *all* the atoms in the simulation you'll just get zero (unless you specified a nett charge in the input files).
And how about calculate the charge transfer? Is this formula correct?
Charge transfer= total charge all (molecule+surface) - total charge (molecule) - total charge(surface)
Thank you so much sir @Philip James Hasnip.
Unless I've misunderstood what you mean, the total charge of the molecule+surface must be the *same* as the total charge of the molecule plus the total charge of the surface, otherwise you've gained (or lost) some electrons from your entire system, which shouldn't be allowed!
Assuming that both the molecule and surface individually would be charge-neutral, then you can just work out the charge transfer by summing the charges of the molecule in the molecule+surface calculation -- any lost (or gained) charge must go to the surface, by conservation of charge. (OK technically it could go into the vacuum, but that isn't going to happen!)
Be warned that charge transfer is often captured rather poorly with the present exchange-correlation functionals, in part because of the self-interaction error which tends to disfavour negative ions.
Thank you so much, sir. You explaination help me a lot. @Philip James Hasnip
Dear all,
I have a late (and probably stupid) question. A CASTEP output file (I mean Mulliken and Hirshfeld analysis) explicitly mentions that the spin units are "hbar/2". But an *.outmol file in DMol3 does not say anything about spin units. Are they the same, that is "hbar/2", or maybe just "e"?
Thank you in advance.
Hi, the DMol3 charges/spins etc are in units of electrons.
All the best,
Felix
Lesego Miya you subtract the "down" population from the "up" population for each atom.
Dear Philip James Hasnip
Can you help me
How to calculate and plot total energy as a function of volume using castep code implemented in biovia materil studio software
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