Questions tagged [quantum-espresso]
Questions related to the open source materials modeling framework, Quantum Espresso.
42
questions
2
votes
0answers
14 views
Plotting density of states of Fe(BCC) using Quantum ESPRESSO
I have tried running DFT calculation and plotting DOS of Fe(BCC) in Quantum ESPRESSO. I have attached the image:
But It's a wrong plot as it is not matching with the referenced DOS plots of Fe(BCC). ...
7
votes
1answer
56 views
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.
5
votes
2answers
45 views
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 ...
4
votes
1answer
63 views
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 ...
5
votes
1answer
40 views
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....
9
votes
1answer
42 views
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 ...
7
votes
1answer
78 views
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 ...
9
votes
2answers
73 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
0answers
40 views
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. ...
8
votes
0answers
67 views
Why are the optical properties of Aluminium so hard to determine?
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 ...
11
votes
2answers
785 views
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 ...
12
votes
1answer
327 views
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 ...
5
votes
0answers
95 views
Is there any way to simulate the Polarization vs Electric Field loop of BaTiO3 using Quantum ESPRESSO?
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 ...
8
votes
1answer
172 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....
8
votes
1answer
66 views
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 ...
10
votes
5answers
544 views
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 ...
9
votes
2answers
147 views
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 ...
10
votes
2answers
405 views
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'...
10
votes
1answer
143 views
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 ...
7
votes
0answers
87 views
Calculating band structure with HSE using Open_grid (Quantum ESPRESSO)
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....
16
votes
2answers
368 views
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?
8
votes
0answers
111 views
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 ...
11
votes
2answers
167 views
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 ...
13
votes
2answers
465 views
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 ...
12
votes
4answers
262 views
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 ...
4
votes
3answers
109 views
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 ...
11
votes
1answer
180 views
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 ...
18
votes
2answers
130 views
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 ...
14
votes
1answer
593 views
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 ...
14
votes
1answer
107 views
Can GW-BSE quasiparticle calculations only be run on norm-conserving pseudopotentials (NCPPs)? If so, why not?
I've read in some texts that GW-BSE quasiparticle calculations have only been implemented on Norm-conserving Pseudopotentials (and not Ultra-soft or PAW PPs). Is there a conceptual reason for this? I ...
14
votes
3answers
280 views
Running Quantum ESPRESSO calculations in Google Colab
So one big problem I experience in doing calculations with Quantum ESPRESSO is that many calculations require a lot of computing power: you need large RAM capacities and powerful processors especially ...
19
votes
2answers
117 views
Norm-Conserving or Ultrasoft, which pseudopotential to choose?
Ultrasoft pseudopotential (USPP), in general, requires a lower energy-cutoff to the plane waves when compared to Norm-Conserving ones (NC). On the other hand (at least with Quantum ESPRESSO) the ...
11
votes
1answer
67 views
Parallelization levels on Quantum ESPRESSO
Quantum ESPRESSO presents several levels of parallelization, including worlds, images, polls, and so on. However, there is a very intricate (and not clear to me) relationship between k-point sampling, ...
17
votes
1answer
193 views
How does the mBJ potential give an accurate band gap as compared to LDA and GGA?
I am not able to understand the literature on how the modified Becke-Johnson(MBJ)$^{[1]}$ potential gives an accurate bandgap. Can someone please help? Thank you. The formula for the potential can be ...
17
votes
1answer
117 views
Why is the band structure of a supercell more dense than for simple cell?
In order to do DFT calculations of metallic alloys, the start point is a supercell, whose atoms are changed to match the desired stoichiometry. Gold and Silver, for example, both have FCC structure. ...
6
votes
1answer
81 views
How to calculate the photoluminescence spectrum from DFT band calculations?
Photoluminescence (PL) spectrum is one of the experimental observable used, among other things, to have an accurate idea about the material band structure.
It can be calculated using the band ...
10
votes
2answers
120 views
How to calculate the effective mass from DFT band calculations?
One of the properties used in Solid State Physics, and specially in semiconductor physics, is the effective mass. It can be calculated from the energy dispersion relationship. The simple form, for ...
22
votes
2answers
394 views
Quantum ESPRESSO vs VASP
We know that both Quantum ESPRESSO and VASP can perform lots of different kinds of simulations of materials. But what can VASP do that Quantum ESPRESSO can not, and vice-versa?
20
votes
1answer
110 views
What is the importance of electron interaction on dielectric response of crystals?
After obtaining the Kohn-Sham orbitals from a plane-wave-based self-consistent-field calculation, the dipole matrix elements could be calculated in order to determine electro-optical properties such ...
12
votes
1answer
107 views
Why is the Nonequilibrium Green’s function (NEGF) method for quantum transport not implemented in plane wave codes like VASP and Quantum Espresso?
DFT codes like Siesta, QuantumATK, Questaal, and Smeagol having localized basis sets have NEGF implementations available. But not in plane wave codes like VASP and Quantum Espresso. Why is it so?
17
votes
1answer
213 views
Are there problems with the Tran-Blaha modified Becke-Johnson potential (mBJ, a.k.a. TB09) in Quantum ESPRESSO?
I have used the modified Becke-Johnson (mBJ) exchange potential before, as it was developed and implemented in Wien2K by Fabien Tran and Peter Blaha (1). In 2013, Éric Germaneau et al. implemented mBJ ...
18
votes
3answers
238 views
How to do periodic DFT calculations using Quantum ESPRESSO?
I have only done quantum mechanical computations using non-periodic wavefunctions. I'd like to try to periodic-wavefunction density functional theory.
Quantum ESPRESSO seems like a good package ...
