[Wien] the results about electron density difference

[Peter Blaha]

For a difference density you have to subtract exactly those states which 
you have in your valence density.
One can influence this by Emin when running lapw2, or in the case.inst 
file (putting manually P for selected states).

By default, Sn 4s,4p and O 2s,2p will be in the atomic density (-sigma),
but you can influence this in the input.

Your case might have Sn-d semicore states and O-2s states close together 
  and you must carefully select an energy Emin to separate them. 
(Eventually it will not be possible at all - in this case you must 
manually edit case.inst and put P into the selected states (eventually 
reducing the "core" and specifying more states by hand so that you can 
put "P" to the Sn-d states.)

yxl at email.jlu.edu.cn schrieb:
> Dear users,
>    I have asked the question last month, but nobody responded.
> I am studying the electron density difference, from where we can know some about the bonding. For example SnO2, the bonding orbital should be Sn:4s 4p, O:2p. But I do not think my following results are reasonable.
>   When I set the Emin in case.in2 to 0.01(Sn:4s 4p, O:2p), the electron density difference located on Sn and O atoms are all minus, and the maxmum is -15.
>   When I set the Emin to -1.0(Sn:4s 4p, O:2s 2p), the electron density difference located on Sn are all positive,the center of O are still minus,but little positive density difference appear around the O atoms. The value is from -1.21~0.5.
> So I have two questions:
> 1.When the Emin became form 0.01 to -1.0, the density should much more and include the density appears in the plot of 0.01. Why the minus density difference located on Sn disappeared, and why the value became to -1.2 from -14?
> 2.The positive density difference on O means that O atoms should get electrons. I think the added electrons should be in O 2p. Why there was no positive density difference on O when Emin was set to 0.01, but appeared when the Emin was set to -1.0?   
> 3.Why the electrons increased for Sn, decreased for O?
> Any suggestions will be appreciated.
> yours sincerely,
> hongxia 
> 
> 
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-- 
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Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
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