Questions tagged [quantum-espresso]

Questions related to the open source materials modeling framework, Quantum Espresso.

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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 ...