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

[Lee, Yongbin [A LAB]]

Hi,
 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. Because you need to count DOS of interstitial region

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?

--> Should be yes.  Because all of them are counting only inside of muffin-tin


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?

--> Again No. Because you need to count interstitial region

Regards,
 Yongbin

________________________________
From: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] on behalf of J. K. Balamurugan [albertbalagan at gmail.com]
Sent: Thursday, March 22, 2012 11:24 AM
To: A Mailing list for WIEN2k users
Subject: [Wien] Questions on the quantitative understanding of DOS and partial DOS

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?

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?

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?

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.




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