Re: [QE-users] Convergence in Hexagonal Systems

2019-02-09 Thread Dr. Thomas Brumme 

Dear Dr. Anuja Chanana,

without more information, we (everyone here in this users list) can't  
help you.
What do you mean with "difficult to reach on convergence"? How do you  
test convergence?


Is an scf cycle not converging? Assuming you calculate a "meaningful"  
structure, this
could either mean you need to increase the wave-function or the  
charge-density cutoff
or both. Or the k-point sampling. Again, I don't think it is a problem  
of the pseudo.
For both N and B, creating pseudos is pretty straightforward and I  
don't think the
pseudos of the PSlibrary are wrong or bad. On the other hand, looking  
at this site:


https://www.materialscloud.org/discover/sssp/plot/efficiency/N

I see that for a nitrogen PBE US pseudo of the PSLibrary a cutoff of  
40 Ry might be
just too small, especially when you want to relax the cell. For  
accurate forces and
pressure you always need a higher cutoff. (PBE is nearly PW91 but for  
the latter, I

guess, you need a higher cutoff)

What do you mean with "its difficult to reach on convergence"?  
Furthermore, why do

you use a smearing if the system is an insulator?

Regards

Thomas

P.S.: Please, always reply to "All", i.e., also to the list, so that  
others can

find the answer if they have the same problem.

Zitat von Anuja Chanana :


Dear Dr. Thomas Brumme,
Thanks for the information.
I tested the pseudopotential for bulk BN hexagonal system as well. But its
difficult to reach on convergence.
PFA the input file.


Thanks and Regards
Dr. Anuja Chanana


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On Sat, Feb 9, 2019 at 10:19 PM Dr. Thomas Brumme <
thomas.bru...@uni-leipzig.de> wrote:


Dear Anuja Chanana,

I don't think it is the pseudo which gives problems in one case and none
in the other. Looking at the structure I guess that you want to
simulate an isolated
layer in the hexagonal system, don't you? Otherwise it would make no
sense to have a vacuum of 6 Angstrom. But then, why do you have only
6 Angstrom? And why do you use k-point sampling in a non-periodic
direction?
Furthermore, your in-plane k-point sampling is different in both systems
which
could explain other differences!? If you really want to simulate a 2D
system have a look at the input variable

assume_isolated='2D'

Otherwise, if you don't want to simulate a 2D system, please check your
structures with, e.g., XCrysDen.

Regards

Thomas Brumme


Zitat von Anuja Chanana :

> Hello all,
> I am trying to converge a hexagonal and cubic system of BN. The cubic
> system shows a convergence while the hexagonal system doesn't, though the
> parameters are the same. I guess there might be some issue in the
Nitrogen
> pseudopotential. Can you please look into the issue?
> PFA the input files for both the systems.
>
>
>
> Thanks and Regards
> Dr. Anuja Chanana
>
>
>
> [image: Mailtrack]
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> Sender
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> 02/09/19,
> 2:41:41 PM

--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig

Tel:  +49 (0)341 97 36456

email: thomas.bru...@uni-leipzig.de






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Re: [QE-users] Convergence in Hexagonal Systems

2019-02-09 Thread Dr. Thomas Brumme 

Dear Anuja Chanana,

I don't think it is the pseudo which gives problems in one case and none
in the other. Looking at the structure I guess that you want to  
simulate an isolated

layer in the hexagonal system, don't you? Otherwise it would make no
sense to have a vacuum of 6 Angstrom. But then, why do you have only
6 Angstrom? And why do you use k-point sampling in a non-periodic direction?
Furthermore, your in-plane k-point sampling is different in both systems which
could explain other differences!? If you really want to simulate a 2D
system have a look at the input variable

assume_isolated='2D'

Otherwise, if you don't want to simulate a 2D system, please check your
structures with, e.g., XCrysDen.

Regards

Thomas Brumme


Zitat von Anuja Chanana :


Hello all,
I am trying to converge a hexagonal and cubic system of BN. The cubic
system shows a convergence while the hexagonal system doesn't, though the
parameters are the same. I guess there might be some issue in the Nitrogen
pseudopotential. Can you please look into the issue?
PFA the input files for both the systems.



Thanks and Regards
Dr. Anuja Chanana



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--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig

Tel:  +49 (0)341 97 36456

email: thomas.bru...@uni-leipzig.de

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[QE-users] Convergence in Hexagonal Systems

2019-02-09 Thread Anuja Chanana 
Hello all,
I am trying to converge a hexagonal and cubic system of BN. The cubic
system shows a convergence while the hexagonal system doesn't, though the
parameters are the same. I guess there might be some issue in the Nitrogen
pseudopotential. Can you please look into the issue?
PFA the input files for both the systems.



Thanks and Regards
Dr. Anuja Chanana



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