Questions tagged [cell-optimization]
For questions regarding optimizations of unit cell dimensions.
25
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2
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0
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Water simulation in ASE/LAMMPS
I want to simulate some water in MD with ASE and a LammpsLib calculator.
I set up a minimal Lammps calculator and I try to calculate the energy per atom of an isolated molecule, and a 3x3x3 supercell. ...
- 667
2
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0
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Why the total energy calculated with GGA and metaGGA=SCAN are so different?
Why the total energy calculated with GGA and metaGGA=SCAN are so different?
My INNCAR file is
...
- 21
1
vote
0
answers
34
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Disappearing liaison when relaxing with Quantum ESPRESSO?
When I optimize the structure, the bonds between carbon atoms disappear, as shown in the figure. What could be the problem?
my input file
...
- 371
2
votes
0
answers
40
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Relaxation of a system with a different Forcefield
I have an amorphous silica surface system with 576 atoms which was generated using BKS forcefield. I would like to relax the system with Reaxff. To do that I use the fixes in lammps as,
...
- 491
4
votes
1
answer
529
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How to restart an interrupted Quantum ESPRESSO calculation?
I was doing a vc-relax calculation and after 1 day the calculation suddenly stopped. Is there a way to restart it from previous interrupted calculation of do I have to restart from the beginning?
- 1,957
4
votes
1
answer
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How to get rotation matrix elements from root integer notation?
For example, I am reading a paper, where they put one layer on top of another, and in order to minimize the lattice mismatch, they transform unit cells of both layers.
They report it in a root integer ...
4
votes
1
answer
407
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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 for the unit cell using Cif2Cell. After that, I ...
- 1,957
5
votes
1
answer
289
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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 ...
- 1,957
2
votes
1
answer
54
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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,...
- 1,957
2
votes
0
answers
94
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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. ...
- 2,742
4
votes
2
answers
270
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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
554
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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
1k
views
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 ...
- 1,117
5
votes
1
answer
126
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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
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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 ...
- 663
3
votes
1
answer
700
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.
- 529
7
votes
1
answer
489
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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: ...
- 465
8
votes
1
answer
539
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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 ...
- 2,561
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...
- 2,561
9
votes
1
answer
904
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 "...
- 5,683
12
votes
1
answer
759
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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 ...
- 2,793
7
votes
1
answer
245
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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
1k
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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 ...
- 2,561
10
votes
2
answers
811
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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 ...
- 4,448
12
votes
1
answer
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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....
- 4,448