[Wien] Choosing proper Emin in electron density plot

[Shu Miao]

Many thanks. This is more instructive to follow.

Shu Miao

======= 2006-10-13 00:37:00 您在来信中写道：=======

> From " Chemistry" it should be clear, that only Ti 3s,3p are 
>"semicore", C 2s belongs already to "valence" states.
>Thus you should put   -1 as EMIN to truncate the semicore for plotting.
>
>I admit, the comment in the scf file:
> > In TiC.scf, there is also "Energy to separate semicore and
> > valencestates:  0.25298".
>is misleading. I should change it to something like "low and high energies"
>
> > This value is consistent with above reasoning.
>No, because C-2 is valence.
>
> > -3.4310763 Ti-3s                correct
> > -1.6693347 Ti-3p                correct
> > -0.1792457 C-2s                 correct
> >  0.7811822 C-2p                 NO
>
>You can easily assign low-E states, because they have mostly "pure" 
>character. It does not really make sense in most cases to assign the 
>"mixed band states", since they will be in general hybridized (Ti-3d + 
>C-2p) and have a large bandwidth (you were looking on just one k-point, 
>for others, this energy can be quite different).
>
>> Dear Wien2k users
>> There are some discussions about setting Emin in case.in2 when plotting
>> the electron density on the mailinglist early this year. Some good hints
>> were given. However, clearer conclusion may be more informative especially
>> for new users, e.g., me. I want to take the TiC as example to work out
>> the right way by following those hints. Please give your advice.
>> In the TiC.scf file, I find the eigenvalues:
>> -3.4310763   -1.6693347   -1.6693347   -1.6693347   -0.1792457
>>  0.7811822    0.7811822    0.7811822    0.8523448    0.8523448
>>  0.8523448    0.8563761    0.8563761    1.4909371    1.7608187
>> The multiplicities for both Ti and C are 1. So I assign the states as:
>> -3.4310763 Ti-3s
>> -1.6693347 Ti-3p
>> -0.1792457 C-2s
>>  0.7811822 C-2p
>> The 5 values around 0.85*** are close but not same, since they are
>> forming band due to bonding effects in solid. They corresponds to the
>> partially-filled valence states Ti-3d.
>> The Fermi level is at 0.73236 just slightly below the C-2p which is not
>> full. So it seems above assignment is correct. An Emin set between
>> -0.1792457~0.7811822 should be able to exclude all semicore states in Ti
>> and C.
>> In TiC.scf, there is also "Energy to separate semicore and valencestates:
>> 0.25298". This value is consistent with above reasoning.
>> However, the value in the UG is -1.0. Why this value? Is there any other
>> consideration I missed? Will a deeper Emin just include a constant
>> part of electron density from semicore states and won't cause big error if
>> we only want to know the difference between different plotting?
>> Please give your advice, whatever it is empirical, technical or
>> theoretical.
>> Thanks
>> 
>> Shu Miao
>> 
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>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>-- 
>
>                                       P.Blaha
>--------------------------------------------------------------------------
>Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
>Email: blaha at theochem.tuwien.ac.at    WWW: 
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