Questions tagged [cell-optimization]
For questions regarding optimizations of unit cell dimensions.
19
questions
4
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0
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84
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What's the appropriate method to create a supercell for Quantum ESPRESSO?
I created a CIF file using the experimental parameters of my material then I used it to create my input file of the unit cell using Cif2Cell. After that I relaxed the structure using 'vc-relax'.
If I ...
- 855
5
votes
1
answer
140
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How to calculate lattice parameter?
After 'vc-relax' calculation I got the cell parameters in the picture bellow. I want to mention that my ibrav=1.
I think the optimized lattice parameter in this case is A=11.44879234*1.006676454 .But ...
- 855
1
vote
0
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25
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Are the cell parameters found after doing a 'vc-relax' calculation the ones used to calculate the material properties?
I created a CIF file using the experimental data from literature . After doing a 'vc-relax' calculation do I have to change the lattice parameter, CELL_PARAMETERS and ATOMIC_POSITIONS in my input file,...
- 855
2
votes
0
answers
43
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Generating unit cell from an optimized molecule in Avogadro?
I am trying to generate the unit cell for a material from the optimized coordinates of a molecule. I am able to generate an orthorhombic unit cell from the coordinates using utilities in Avogadro. ...
- 715
4
votes
2
answers
144
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VASP structure relaxes to an incorrect ground state
I am using VASP to perform a structural relaxation of $\ce{CuNCN}$. I am using the PAW-PBE POTCAR files for the same and the KPOINTS have been generated using a script. The POSCAR file has been ...
- 235
6
votes
1
answer
303
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Converging geometry of iron slab
I am a sort-of-beginner in Quantum Espresso. I do understand certain terminology in the INPUT file but I am faced with a dilemma. I have been trying to optimize $\ce{Fe}(110)$ system of 100 atoms ...
- 149
7
votes
1
answer
606
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Meaning of lattice parameters in vc relax calculations
I am performing vc relax calculations to find the effect of pressure on the cell. Both tensile and compression pressure. But I am confused about the lattice ...
- 1,015
5
votes
1
answer
111
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What's the Difference between Lattice Statics and Lattice Dynamics?
For example, in something like the General Utility Lattice Program, you perform structural optimisation and then use phonons to calculate properties like elastic constants etc.
The latter part seems ...
- 929
8
votes
3
answers
420
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Cu FCC vc-relax method error
Reference: Density Functional Theory: A Practical Introduction, David Sholl, Janice A. Steckel, Chapter 2, Page No. 48
Section 2.2 The fcc Cu calculations in Fig. 2.3 used a cubic supercell
with 4 Cu ...
- 643
3
votes
1
answer
434
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How to do lattice optimization, encut optimization and Kpoint optimization in VASP?
What is the procedure to do lattice optimization, encut optimization and kpoint optimization in VASP?
Thank you in advance.
- 519
7
votes
1
answer
314
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What parameters have to converge before doing a relax calculation?
I am a beginner of Quantum Espresso. I have taken 221 MoS2 Monolayer and done a relax calculation.
In case of bulk system, or any doping in supercell, which is preferred: ...
- 455
8
votes
1
answer
328
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Why volume of unit cell is not the same as cubing the lattice constant?
I have a cubic-FCC with a=b=c and $\alpha$=$\beta$=$\gamma$=$90^o$. As far as I understand the volume of this cubic unit cell should be a cube of the lattice constant. But this not the case I am ...
- 2,481
9
votes
2
answers
2k
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Pressure applied DFT calculations in Quantum ESPRESSO
I am trying to perform the pressure-induced DFT calculations in Quantum ESPRESSO. For this, I have calculated the lattice constant of the cubic structure by vc-relax...
- 2,481
8
votes
1
answer
561
views
In VASP, which option is better for monolayer relaxation: ISIF=3 or ISIF=4?
Since I have started working on monolayers I was using the ISIF=3 tag for relaxation, this was after recompiling VASP with the modified "...
- 5,593
12
votes
1
answer
578
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Structure relaxation of a thin film structure in VASP
I have some general questions about doing the structure relaxation of a thin film structure in VASP. I want to study the how the band structure evolves as we increase the number of layers of the ...
- 2,763
7
votes
1
answer
206
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Smearing and charge balance for tungsten with interstitial oxygen in Quantum ESPRESSO
What smearing would be ideal for a bcc W with interstitial O atom. I am running 3x3x3 unit cells with one N interstitial.
I am having convergence issues in relax ...
- 457
12
votes
2
answers
820
views
Getting different total magnetic moment in 'scf' and 'vc-relax' calculations in Quantum ESPRESSO
I am performing a spin polarized DFT calculations in Quantum Espresso on a Co2MnSi ferromagnetic crystal. For this I have performed these steps:
1) Performed ...
- 2,481
10
votes
2
answers
634
views
Should I do vc-relax with nspin=2 in Quantum Espresso for magnetic samples?
I'm a beginner when it comes to DFT and Quantum Espresso.
Consider I have a lattice which has associated magnetic properties. So for geometric optimization should I take into account the magnetic ...
- 4,308
12
votes
1
answer
5k
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When should "vc-relax" be performed over "relax" calculations in Quantum ESPRESSO?
I'm new to Quantum ESPRESSO and I have read that there are several scenarios when relax calculations are preferred over vc-relax calculations, for example in maintaining vacuum while modelling surface....
- 4,308