[Pw_forum] some problem in lowdin charges

[Stefano Baroni]

Dear Mr. unnamed:

Lowdin charges (as well as other conventional atomic charges) do not  
satisfy any sum rule. You can easily convince yourself that ths is the  
case because the atomic orbitals that are used to calculate them are  
arbitrary to some extent. If yu like, you can think that the missing  
charge is "delocalized" or "bonding" charge, but this would be another  
way of naming the conventional (to some extent) character of Lowdin  
charge.

Please, do not forget to use the courtesy of signing your  
correspondence to this forum amd of providing your academic affiliation.

Have a good day
SB

On Sep 17, 2008, at 3:55 AM, huangchunlin1984 wrote:

> Doctor:
>        I have done Lowdin population analysis on the Fe clusters.  
> From the Lowdin charges, I find that the total charge of the cluster  
> is a little lower than the accurate value. Take the Fe3 cluster for  
> example,using 3d4s for Fe.
>     Lowdin charges:
>         Atom # 1: total charge = 7.8407   ...
>         Atom # 2: total charge = 7.8407   ...
>         Atom # 3: total charge = 8.0938   ...
>     The sum charge of the three atoms is 23.7752 which is not 24. So  
> where is the other charges ? Or is this accurate enough ?
>     the input is as follows:
>       &inputpp
>          outdir='./'
>          prefix='Fe3'
>          Emin=-8.0, Emax=-1, DeltaE=0.1
>          ngauss=0, degauss=0.001
>        /
>                                             thanks for your help.
>
>
>
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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