[Wien] Questions on the quantitative understanding of DOS and partial DOS

[David Tompsett]

Dear Balamurugan,

Some answers below and many previous postings:

On Thu, Mar 22, 2012 at 4:24 PM, J. K. Balamurugan
<albertbalagan at gmail.com>wrote:

> Dear WIEN2k developers and users,
>
> I have some problem in quantitative understanding the DOS and partial DOS
> plots/data. I post the question with a case assumption of room temperature
> (RT) structure of BaTiO3. As it is well known BaTiO3 has tetragonal
> structure at RT. Now, Ba and Ti has one site and O has two sites. If the
> DOS & partial DOS are calculated for BaTiO3, I will get total DOS for the
> unit cell which contains one formula unit of BaTiO3. I will also get
> partial DOS of Ba, Ti and O1 and O2 (in terms of total and from individual
> orbital contribution like s, p and d whichever are applicable.) Here are my
> questions:
>
> 1. Will the sum of total DOS individual atoms [i.e., total DOS of (Ba + Ti
> + O1 + O2)] be exactly equal to total DOS of the unit cell? If the answer
> is No, why?
>
No, the interstitial states contribution is missing. Only the area inside
the muffin tin is included in the partial DOS.

>
> 2. Will the total DOS of any specific atom, say Ti, will be exactly equal
> to the sum of orbital contributions [i.e., partial DOS of (Ti-s + Ti-p +
> Ti-d)]?  If the answer is No, why?
>
Yes, but I think even further depending on how many l-values are in the
basis set.

>
> Another related question: Let us assume a hypothetical structure where in
> I have two formula units of BaTiO3 in a unit cell. That is the unit cell
> has Ba2Ti2O6. Now the question is the following:
> 3. Should I need to multiply 2 to the total DOS of individual atoms {i.e.,
> 2*[total DOS of (Ba + Ti + O1 + O2)]} to get the total DOS of the unit cell
> with two formula unit? Will this sum be exactly equal to the actual total
> DOS of the unit cell which we get as it is from the calculations?
>
Yes. Then no not total DOS of cell, see point 1.

>
> Please explain me to clear these my questions. I wish also to get into
> reading any material/user guide/article/document which could help me to
> have a complete understanding on this issue.
>
> Thanks.
>
> With kind regards,
> K. Balamurugan.
>
>
> David Tompsett.

>
>
> --
> *K. Balamurugan
> Pittsburgh, USA.
> +1 412 961 5055*
>
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>
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