Questions tagged [quantum-espresso]
Questions related to the open source materials modeling framework, Quantum Espresso.
42
questions
21
votes
3
answers
634
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 ...
- 7,869
20
votes
3
answers
3k
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 ...
- 5,593
28
votes
2
answers
4k
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?
- 3,148
21
votes
9
answers
8k
views
How to master Fortran with minimal effort?
Fortran language is used in many first-principles matter modeling codes, such as VASP and QE. These codes usually include many ...
- 14.6k
19
votes
1
answer
2k
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. ...
- 3,148
18
votes
2
answers
4k
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 ...
- 1,471
17
votes
1
answer
888
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 ...
- 4,487
14
votes
3
answers
5k
views
Should I connect 2-3 laptops to form a supercomputer?
I have recently started to use Quantum ESPRESSO for evaluating different properties of ZnSe Quantum Dots. But I currently don't have access to any cluster and as I am increasing the size of ...
- 1,641
13
votes
4
answers
2k
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 ...
- 131
12
votes
1
answer
306
views
What is the best program to manipulate numerical DFT wavefunctions to calculate custom matrix elements?
For pedagogical reasons, I am looking for ways to calculate quantum-mechanical quantities such as $\langle m | \dot{m}\rangle, \langle m | \dot{n}\rangle, \langle m | \ddot{n}\rangle$ using ...
- 2,131
12
votes
2
answers
5k
views
What is the difference between DOS and PDOS?
I'm new to DFT. Can you please help me to understand DOS and PDOS (projected density of states) in simple wording? I only want to know some basics of these terms and how they are linked to DFT.
- 121
9
votes
1
answer
4k
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 ...
- 2,481
8
votes
1
answer
350
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.
- 4,298
5
votes
1
answer
226
views
Convert PSP8 pseudopotential files to UPF format
Is there a way to convert psp8 pseudopotential files (used for abinit) to UPF format (used for Quantum ESPRESSO)? I noticed there is the upfconv.x utility in ...
- 151
22
votes
2
answers
4k
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?
- 5,593
20
votes
2
answers
815
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 ...
- 3,148
19
votes
3
answers
2k
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 ...
- 1,121
18
votes
2
answers
270
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 ...
- 1,336
17
votes
1
answer
804
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 ...
- 676
13
votes
5
answers
6k
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 ...
- 2,481
12
votes
1
answer
338
views
Recommended code to do XAS/XES/RIXS calculations with?
I am a grad student looking to simulate several XAS/XES and potentially RIXS spectra for some strongly correlated metal-oxides. The materials in question will likely require solving the Bethe-Salpeter ...
- 221
12
votes
3
answers
1k
views
How can I submit jobs to an HPC scheduler?
It is my first time trying to use an HPC system and I am a bit overwhelmed. I have gone through a course on using HPC systems on Coursera and have a basic idea about using Linux. Could you guys tell ...
- 1,641
12
votes
1
answer
870
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?
- 8,612
12
votes
1
answer
5k
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....
- 4,298
11
votes
1
answer
222
views
Geometrical Optimization not converging, where am I going wrong?
I am trying to obtain the optical properties of ZnSe Quantum Dots, the problem is that my geometrical optimization is not converging. I used VESTA to create the structure(there is a photo in the ...
- 1,641
11
votes
1
answer
2k
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 ...
- 2,481
11
votes
2
answers
1k
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 ...
- 2,481
10
votes
1
answer
927
views
How to understand the wavefunction outputed by QE with HDF5 format?
Following the answer to my question: What is the best program to manipulate numerical DFT wavefunctions to calculate custom matrix elements?,
I compiled Quantum ESPRESSO with the hdf5 flag on, and now ...
- 2,131
9
votes
1
answer
264
views
Should I use a lower threshold for calculations involving SOC?
I'm studying a compound $\ce{VSe_2}$ using the DFT package Quantum ESPRESSO (QE). The following is the input file.
...
- 947
9
votes
1
answer
697
views
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]...
- 4,298
9
votes
3
answers
2k
views
Installing Quantum ESPRESSO on an Apple M1 processor possible?
I'm attempting to make QEspresso's pw program on a new 2021 MacBook Air, which has an M1 processor. While ./configure does not throw any errors, running 'make pw' fails with the following output:
<...
- 633
8
votes
3
answers
418
views
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
8
votes
1
answer
173
views
Do NSCF calculations on Supercell gives different band gap than the Unit Cell?
NSCF (non-self-consistent field) calculations are done on a dense mesh. I did it on a unit cell. Then since I have to try using a supercell for alloying, I am doing calculations to see the results of ...
- 1,015
8
votes
0
answers
158
views
Bloch wave function extraction for the specific k-points and specific band from QE calculation [closed]
I would like to use QE to obtain u_K(r), which is the Bloch wave function of spin-up maximum valance band at K point. If I define the K point in the input file and do an SCF calculation by QE ...
- 81
7
votes
1
answer
991
views
Running Quantum ESPRESSO on a GPU in Windows
I have been using BURAI GUI for Quantum ESPRESSO for the calculation of optical properties of ZnSe. While running calculations I observed that my laptop's GPU was not even being used and I am a bit ...
- 1,641
5
votes
0
answers
174
views
Cif2QE (QEtoolkit): Error when using this input file for (221) MoS2 monolayer [closed]
My input file for the (221) $\ce{MoS2}$ monolayer was created through Cif2QE (QEtoolkit):
...
- 455
5
votes
1
answer
141
views
How to make ferro, feri and antiferro magnetic structure for QE
I have below &SYSTME information from my input file
...
- 1,663
3
votes
0
answers
49
views
Cutoff energy in Quantum ESPRESSO calculation [duplicate]
What is cutoff energy in solid state calculations? I would just like a detailed explanation and the applicable formulas!
- 3,701
3
votes
1
answer
78
views
Quantum transport in device (Transiesta code)
I want to understand how the current (or electron) is normally transported in a device like a graphene, under the Transiesta code. It is based on which principle: a gate is applied, or there is a ...
- 309
3
votes
0
answers
348
views
What input setting in Quantum ESPRESSO will allow me to calculate the free energy of a solid? [closed]
I understand that it's possible to calculate the Gibbs free energy of a system ab initio, see for example: How can we calculate the Gibbs free energy from first principles?
I'm wondering how I can do ...
- 3,701
2
votes
1
answer
75
views
Need help about how I can get/generate semicore pseudopotentials to be used in Quantum Espresso DFT?
I would like to know if I can get/generate semicore pseudopotentials (some core electrons are also considered along with valence electrons) to be used in Quantum Espresso DFT. Actually, it would be ...
- 643
2
votes
1
answer
101
views
I'm considering to take an introduction course with textbook "Materials Science and Engineering: An Introduction", as a beginner QE user. Is it okay?
People, I am a beginner in material modeling (I am studing solid state in Quantum ESPRESSO) and I am having a lot of difficulty with basic terms like "k-points", "Miller Indices", &...
- 361