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Topics - quantumtoday

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1
General Questions and Answers / Build Hexagonal Closest Packed structure
« on: December 13, 2017, 00:50 »
Hi all,

I want to build a HCP structure 6 atoms/cell from the primitive cell 2 atoms using the VNL builder. How can I do it? Please advise.

Thank you.



2
General Questions and Answers / Choosing approriate pseudopoptentials
« on: April 3, 2017, 10:46 »
Hi all,
In case we have an overlap structure with the middle part made of bilayer structure, and the others made of single layer structure, for instance:
(top layer)            -------------------------------------------

(bottom layer)                                             ------------------------------------------
How should we choose pseudopotentials for DFT calculations?  simply choosing pseudopotentials with GGA, LDA or it should be vdw or even both?



 

3
General Questions and Answers / Is that ok to do MD relax then put the relaxed coordinate for DFT calculations?
« on: February 10, 2017, 16:46 »
Dear all,

Relaxation with DFT is usually expensive, particularly for large structures and/or including defects. With vacancy inclusions, many times I can not get relax convergence with QE and Siesta.

So, my question is that: is that ok to do MD relaxation with VNL and then take the relaxed coordinates for other DFT calculations? Is that still safe?

Any ones with experience about this problem, please give comments and advices.

Thank you.

4
General Questions and Answers / hard to remove nagative phonon bands when using classical potential
« on: February 10, 2017, 10:58 »
I re-post my question/concern about phonon bands with classical potential here:

it seems very hard to remove negative bands of graphene if using the potential tersoff_C_2010 (even the structure was optimized). Did you succeed in using this potential?

My concern is that is there any rule when optimizing structures to be sure that negative bands will go away just by one or two times of optimization?

5
General Questions and Answers / Viewing the final coordinates of QE relax
« on: February 3, 2017, 13:56 »
Dear VNL developers,

It seems that VNL does not use the final coordinates of relax in QE calculations as I view result relax.out with "viewer". When I selected the file "relax.out" and chose "Text Representation" I saw the coordinates are the initial ones.

I can make a trick by copying the final coordinates into the cif file, so I can view the relaxed structure. However, I expect we can view the relaxed structure directly from the file "relax.out" without further effort. Is that possible to do with the current version of VNL (or QE plugin) or it will be fixed in next versions?


 




6
General Questions and Answers / VNL and phonon band QE
« on: January 15, 2017, 01:50 »
Can VNL show the phonon band with data calculated by quantum espresso?

7
General Questions and Answers / color of spatial regions
« on: November 8, 2016, 16:38 »
Hello ATK developers,

Can I choose a color  (as I prefer) for an added spatial region?

Thanks.

8
General Questions and Answers / VNL needs much time to finish loading projects
« on: October 17, 2016, 10:15 »
Dear all,

Has any one experienced that VNL took much time to finish loading projects? Few days ago, it was still normal but now it takes me about 8 minutes to finish loading projects on my Windows 10 platform. I am using VNL 2016.2 ( I do not have this problem on Linux).




9
General Questions and Answers / VNL - effective mass
« on: October 10, 2016, 17:40 »
Dear alls,

Is it possible to use VNL to calculate effective mass from data of energy bands calculated by Quantum Espresso or other codes?

My first check, it is not. However, I think there is some way to do this. Please suggest if you know.

Thank you.

Sincerely,
Tran


10
General Questions and Answers / xyz input and output files with VNL
« on: October 10, 2016, 17:16 »
Hi,

I would like to ask about problems of xyz input and output files using with VNL:

- If I download a xyz file from somewhere (for example, http://materia.fisica.unimi.it/manini/dida/structures.html) and open by VNL, I do not see the periodic propertiers of the structure and can not repeat unit cells using "bulk tools" in Builderor and also can not view BZ.
- Similarly, If I create a periodic structure in VNL using the existing database, and then export to a xyz file. Then I import this xyz file in Vesta or Xcrysden, I can not repeat unit cells.

So do you know why I did have this problem? How can I fix it?

Many thanks.

Sincerely,
Tran

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