Questions tagged [quantum-espresso]
Questions related to the open source materials modeling framework, Quantum Espresso.
313
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Is it necessary to terminate the surface ions in a quantum dot? [closed]
I was trying to study quantum dots of ZnO. But I'm pretty new to creating and passivating 0-dimensional particles. Is it always necessary to passivate the free surface of the quantum dot? Regarding ...
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10
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2
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785
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How to perform charge analysis for a molecule
I am doing dehydrogenation of a molecule (say $\ce{C12H12}$) and I want to do charge analysis for dehydrogenated system ($\ce{C6H6}$). How I can proceed? I can use Quantum ESPRESSO and Gaussian ...
- 1,663
9
votes
2
answers
691
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inconsistent behavior between band structure and density of states
I'm a beginner in DFT calculation. I have performed a DFT calculation on CuCoSnSe using PBE-GGA on Quantum Esspresso. When I plot the band structure and the total DOS, the band structure shows a ...
- 717
7
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1
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286
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Incosistent charges and magnetic moments between SCF and PDOS calculations in Quantum Espresso
I have a system of 5 layers of an element + 1 layer of another one, I want the relaxed position of the last layer, and once I have it, proceed to calculate the pdos. I am performing simulations in the ...
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7
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1
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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
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2
answers
867
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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 ...
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18
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4
answers
2k
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Is it possible to calculate the Curie temperature for magnetic systems?
Using DFT calculations we can know the electronic and magnetic property of the system at 0 K. I am wondering if there is any computational method to know the curie temperature of magnetic materials? ...
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784
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Is the "Final Magnetic moment" in the materials project repository same as the "total magnetization" value in Quantum ESPRESSO output files?
I'm quite new to spin-polarized DFT and have been trying to study $BaVSe_{3}$ which is ferromagnetic (with a Final Magnetic Moment of 0.052 Bohr Mag) as per the Materials Project repository [picture 1]...
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11
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How to analyze the band symmetry with Quantum ESPRESSO?
This question is related to this paper: J. Phys. Chem. Lett. 2017, 8, 13, 2999–3007
The above figure shows symmetry analysis for the band structure. The author writes:
The band symmetry and parity ...
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Relax vs VC-Relax for interstitial incorporation energy
In order to model an interstitial trapped in a metal lattice, and the associated incorporation energy, which should be used - "relax" or "vc-relax"? I want to understand the ...
- 457
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Is there a difference in performance when the symmetry is specified via ibrav in Quantum ESPRESSO?
I have been using cif2cell for converting CIF files into quantum ESPRESSO input files. But cif2cell always keeps the ibrav value to be zero and indicates the CELL_PARAMETERS. As per the quantum ...
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13
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2
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814
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Deciding the number of CPUs for a DFT calculation for band structure in Quantum ESPRESSO?
If I am using Quantum ESPRESSO for bandstructure calculations, how can I know the number of CPUs necessary for such a calculation? I deal mostly with ternary transition metal oxides which have at ...
- 131
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How many GB of RAM would be needed for VASP to evaluate optical properties of a material?
Even though it is a powerful tool, Quantum ESPRESSO's hardware requirements are very high. For instance, to evaluate optical properties, even for structures with tens of atoms, Quantum ESPRESSO can ...
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How to choose starting magnetization while doing spin polarised calculation in Quantum ESPRESSO?
I am trying to run spin polarised DFT calculation in Quantum ESPRESSO on system Co2MnSi. I kept starting magnetization for all these three species as,
...
- 2,481
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1
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836
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How to calculate the energy of conduction band and valence band with respect to vacuum in quantum espresso?
I was able to calculate band energies in quantum espresso. How to convert them to values that are in terms of difference from vacuum energy?
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Can you list some useful code snippets for processing quantum ESPRESSO output files?
I know that this is quite general. But we have all written code for processing output files from various dft codes. The functionality of which, may range from analysing time traces to finding ...
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Spin polarized DFT calculation in Quantum ESPRESSO
I am trying to run spin polarized DFT calculation on system Ti2FeSn.
I am doing vc-relax calculation to relax the unit cell but having problem to converge total energy. Total magnetization is also ...
- 2,481
17
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2
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What is nscf calculation in Quantum ESPRESSO?
I have been using 'nscf' for DOS calculation since it is faster and therefore possible to use a higher kpoints. But why is it faster? why not use it in the place of 'scf'?
- 1,521
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1
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996
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How to model electric field in Quantum ESPRESSO?
I have seen papers that take change in Gibbs Energy by just adding a 'eU' term where U is the potential applied. Is there any better way to do this in Quantum Espresso? And is the former way accurate ...
- 1,521
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838
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How to apply solvent model in Quantum ESPRESSO?
In many cases especially when it comes catalysis (which is what I work in) the effect of solvent comes into effect. I have seen papers that takes into account water as solvent by adding a number of ...
- 1,521
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657
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How to separate the band structure of different materials in heterostructures using Quantum ESPRESSO?
So, I know that to calculate surface band structure of a material, you have to take its 2D system eg. single or few-layered. But, how to find the surface band structure in the case of heterostructures....
- 1,521
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Plotting density of states of Fe(BCC) using Quantum ESPRESSO
I have run the DFT calculation and plotted DOS of Fe(BCC) in Quantum ESPRESSO. I have attached the plot:
(click on image to see clearly)
But It's a wrong plot as it is not matched with the referenced ...
- 2,481
8
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1
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389
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How to extract the Pressure, Energy and unit-cell volume from quantum ESPRESSO output file using bash script?
I needed the Energy and Volume values for predicting the bulk modulus of a crystal via the Birch Murmaghan equation. Can I get a bash script for doing the same.
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2
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382
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How can I increase the default maximum limit on step size for convergence in quantum ESPRESSO?
When trying to manually optimise the geometry of the crystal, I've faced an issue wherein the code stopped the convergence process after just 100 steps (which was the default maximum). Is there a way ...
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1
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How to use the ev.x tool in Quantum ESPRESSO?
The requirement I have is to calculate the bulk modulus from the energy values at certain volumes obtained via DFT calculations. Can you provide the instructions to use the ev.x tool in the Quantum ...
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376
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How to resolve the cif2cell TypeError?
I have encountered an error using cif2cell while covering a CIF file from COD to quantum ESPRESSO format. The error is as follows.
command typed:
$cif2cell crystal.cif -p quantum-espresso -o crystal....
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9
votes
1
answer
638
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Quantum ESPRESSO: parameter "assume_isolated": is it applicable to slabs?
I am studying atomic slabs which are periodic in 2 dimensions. Normally in the third dimension, I add a vacuum layer and use dipole correction to mimic proper boundary conditions. Recently I have ...
- 300
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1
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What is the physical meaning of occupations='smearing' in Quantum ESPRESSO?
I want to understand, what is the intuition behind using the occupations='smearing' or 'tetrahedra' in Quantum ESPRESSO input file? I mean how we can interpret what is going to happen inside of ...
- 2,481
10
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2
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675
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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 ...
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8
votes
1
answer
81
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How to predict new Half Metallic materials with higher degree of spin polarization?
Using DFT calculations, how one can predict the new half metallic materials with higher degree of spin polarization. I want to know the steps which have to be followed in prediction of new materials. ...
- 2,481
11
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1
answer
195
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Are there any other options beyond increasing the k-sampling and the number of unoccupied bands, to achieve better results?
I am trying to determine the optical properties of bulk Aluminium and related alloys using Quantum ESPRESSO. I am using both the epsilon.x and the simple.x modules to get wavelength-dependent ...
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11
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2
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1k
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Is there an energy gap correction factor that needs to be used in DFT calculations?
I am a beginner and have performed the DFT calculation in Quantum ESPRESSO for calculation of the direct and indirect bandgap of Silicon. I found the indirect bandgap to be 0.6551 eV. Now, I have ...
- 2,481
13
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1
answer
692
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Si energy band values are not matching with literature values
I have performed the DFT calculation for Silicon in Quantum ESPRESO. I have tried to calculate the electronic band structure, the shape of wiggles of bands are mostly matching but the energy values ...
- 2,481
6
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268
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Is there any way to simulate the Polarization vs Electric Field loop of BaTiO3 using Quantum ESPRESSO? [closed]
I'm new to the Quantum ESPRESSO package. There are articles outlining the procedure of indirectly simulating the P-E loop of piezo-electric materials via Berry phase calculations.One procedure is ...
- 4,338
12
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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....
- 4,338
11
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1
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How to do spin polarization calculations using Quantum ESPRESSO?
I am currently new to DFT calculations in Quantum ESPRESSO. Though, I have read some research papers for determining spin polarization and Half-metallicity in certain Heusler alloys. These research ...
- 2,481
13
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5
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7k
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How to know optimal K-points grid values for good DFT calculation?
I am doing DFT calculations with pw.x executable in Quantum Espresso. For this we have to choose right K-points grid in order to perform error-less calculation. But I have no idea about how can I ...
- 2,481
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2k
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How to choose pseudopotential for DFT calculations in Quantum ESPRESSO?
I am a beginner and newly started running DFT calculations to find out the electronic band structure of certain materials in Quantum ESPRESSO. But we have to select the pseudopotential for running the ...
- 2,481
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2
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3k
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When should spin polarized calculations be done?
Should the presence of a d block element in the unit cell mandate the need for performing spin-polarized calculations? I wanted to find out the DOS, PDOS, and the band structure. I'm new to DFT and I'...
- 4,338
12
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1
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934
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Increasing supercell size to increase K-points sampling
Suppose I have a system with a property that is highly dependent on the density of k-points, namely the dielectric function. Using a small supercell, say with 4 atoms, I've reached the maximum allowed ...
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7
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648
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Calculating band structure with HSE using Open_grid (Quantum ESPRESSO) [closed]
I have executed the SCF calculation and obtained the results. After which I used kmesh.pl to extract k-points. I was able to run wannier calculations but there was an error
Checking info from wannier....
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What are some good band-structure/DOS plotting tools/styles?
I am currently using p4vasp for drawing DOS and band-structure plots, but it is not much handy in modifying the OUTPUTS. Could you please suggest any other good software or tools for that?
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329
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How do I predict the structure of a nanoparticle with Calypso and Quantum ESPRESSO?
I want to create a nanoparticle of CuO and predict it's structure. I've done unit cell relaxation with Quantum ESPRESSO. One tool to predict nanocluster structure is Calypso which is PSO-based. I'm ...
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What is the difference between Ultrasoft, ONCV and PAW Pseudopotentials? Which is better for a spin-orbit coupled calculation?
I am trying to do spin-orbit coupled calculations for various topological insulators. I have found papers using Quantum Espresso with ONCV pseudopotentials and papers using VASP with PAW ...
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3
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3k
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k-points and ENCUT convergence tests before or after relaxation?
Let's say I want to relax a structure using VASP. K-points and ENCUT convergence tests must be conducted before or after relaxation? and which tags should be ...
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4
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2k
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How to make a k-point convergence test for a bulk structure with a lower k-point in the z-direction?
Let's say I want to make k-point convergence test for graphite. And let's say it converges at 12x12x4.
Do I first need to do a k-point convergence test for equal k-points on xyz directions then make ...
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3
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DFT code for quantum simulation of atomic heat transport
I am interested in studying material heat transport using Density Functional Theory. Searching, I found a work1 about using ab initio equilibrium molecular dynamics (AIMD) as implemented in ...
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11
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1
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265
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Is there any software that can generate the electronic DOS of GaAs?
I want to calculate the density of states of GaAs conduction band (preferably each valley like Gamma, L and X). Is there any software available where I can easily generate DOS?
Has the DOS of GaAs ...
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307
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Calculating binding energy between two systems
Regarding the calculation of binding energy of molecular absorption on graphene, for which this has been discussed before, the process of calculating $E_{AB}$ is fairly straight forward, i.e., it is ...
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Calculating HSE06 band structures on Quantum ESPRESSO
I am currently trying to figure out how to compute band structures for my system, using the hybrid functional HSE06. I'm doing this on Quantum Espresso. As I understand, there are a handful of ways to ...
- 2,376