Questions tagged [cell-optimization]

For questions regarding optimizations of unit cell dimensions.

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12
votes
2answers
385 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 ...
12
votes
1answer
195 views

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 ...
11
votes
1answer
1k views

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....
10
votes
2answers
297 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 ...
8
votes
2answers
522 views

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...
8
votes
1answer
179 views

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 ...
7
votes
1answer
129 views

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 ...
6
votes
1answer
74 views

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: ...
6
votes
0answers
89 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 "...
3
votes
1answer
89 views

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.