[Wien] Partial charges inside atomic spheres

[Jorissen Kevin]

To your second question :
 
charge transfer observed in calculations is always a lot smaller (easily a factor of 10, say) than the formal valence would suggest.
Also, there are many ways to define the charge of an atom (and none of them is 'right', since atoms don't exist anyway ...), so one must be very careful when interpreting the numbers.
 
I would do the calculation not only for the particular compound that interests me, but also for similar compounds of which the valence is 'well established' (ie, something with CU2+ and something with Cu4+), and then compare the numbers - it is safer to interpret tendencies than numbers.
 
It is then still up to you to decide in what way you are going to measure charges - muffin tin integration?  Bader?  Mulliken?  RA?  Stockholder? ...
I personally like the concept of Bader charges, but not everyone agrees.
  
 
Kevin Jorissen
 
EMAT - Electron Microscopy for Materials Science   (http://webhost.ua.ac.be/emat/)
Dept. of Physics
 
UA - Universiteit Antwerpen
Groenenborgerlaan 171
B-2020 Antwerpen
Belgium
 
tel  +32 3 2653249
fax + 32 3 2653257
e-mail kevin.jorissen at ua.ac.be
 

________________________________

Van: wien-admin at zeus.theochem.tuwien.ac.at namens stargmoon
Verzonden: wo 24-11-2004 17:56
Aan: wien at zeus.theochem.tuwien.ac.at
Onderwerp: [Wien] Partial charges inside atomic spheres


Dear Prof. Blaha and wien community,
 
To Prof. Blaha: In your paper Phys. Rev. B vol 67, p075102 (2003), table 1 shows the partial charges for one spin direction calculated inside the atomic spheres. I don't understand why the Cu s charges are larger than 1, and Cu p charges are larger than 3. Is this contradictive to Pauli repulsion principle? If not, what do the partial charges inside the atomic spheres stand for?
 
To wien community: Can we estimate the valence state of each atom in an ionic compound from first-principles calculations? For example, in the case of La2CuO4, if we just consider the neutral condition, we have two possible choices assuming oxygen takes its normal ionic state O2-: 
1, La takes its 2+ valence state, Cu takes its 4+ 
2, La takes its 3+ valence state, Cu takes its 2+ 
Can we determine which one is the most possible choice from our ab inito calculations?
 
Looking forward to your reply.
 
Thanks in advance!
 
Best,
 
Stargmoon

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