Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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what determines the 'Estimated total dynamical RAM ' in a Quantum Espresso calculation

As per my understandings the computer resources required for a DFT calculation increases by an order of three with the number of atoms. But as you can see in the output files given below the ...
Joyal sunny's user avatar
3 votes
1 answer
95 views

Is it possible to do a vc-relax calculation using GPAW?

I wanted to do a variable-cell relaxation calculation using GPAW (similar to the one present in quantum ESPRESSO). It would be nice if I could get pointers on how to approach this. ...
Atom's user avatar
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4 votes
1 answer
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Introducing a vacuum space in z direction for 2D monolayer calculations

Is the introduction of a vacuum in the z-axis necessary when utilizing a 2D monolayer material for Density Functional Theory (DFT) calculations in Quantum Espresso? (This is due to the fact that only ...
Thejan Hasaranga's user avatar
3 votes
0 answers
29 views

How to undo the periodic boundary conditions for supercell calculations

I am using Quantum Espresso to study defects in III-V materials, and recently I relaxed my defect system in a 64-atom supercell. Currently, I am trying to determine the ionic displacements relative to ...
Austin's user avatar
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2 votes
0 answers
24 views

PDoS using mBJ in vasp

I have calculated the band structure of a compound using mBJ-LDA potential and plotted it using the p4vasp package. However, i am not able to get Partial DoS from these calculations. I have followed ...
Vivek Gusain's user avatar
4 votes
1 answer
80 views

Can we use Density Functional Theory (DFT) to calculate the second and third-order force constants of a slab?

If we aim to compute the surface phonon lifetime of a Cu(111) surface, the second and third-order force constants are essential (to put in Boltzmann transport equation). However, to my knowledge, it ...
James's user avatar
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8 votes
2 answers
101 views

What is the Kohn-Sham Hamiltonian?

I am trying to understand the adiabatic connection as motivation for hybrid functionals that include Hartree-Fock like exchange. While it sounds intuitive that the exchange of the noninteracting Kohn-...
Hans Wurst's user avatar
8 votes
1 answer
257 views

Comparing results of various DFT calculations in Quantum ESPRESSO

To verify the reliability of calculation scheme, I want to compare lattice constants, bond length and band gap calculated by the different functionals with the experimental results. So in order to do ...
Joyal sunny's user avatar
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0 answers
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Short-range ordered high entropy alloys

I want to create a high entropy alloy with short range ordering. Is there any way achieving this by using ATAT? The mcsqs code only gives random solid solutions.
Nana Kofi Boakye's user avatar
3 votes
1 answer
65 views

Identification of all possible H adsorption sites on the surface

I want to calculate Gibbs free energy of hydrogen atom adsorbed on an adsorption site (ΔGH*), to evaluate the HER activity of that particular surface of material. How can i identify all possible H ...
Joyal sunny's user avatar
2 votes
1 answer
33 views

vc-relax calculation on two-dimensional slab

Is performing only a relaxation calculation (calculation='relax') sufficient for geometrical optimization in conducting a density functional theory (DFT) study of ...
Joyal sunny's user avatar
4 votes
1 answer
62 views

Non-monotonic behaviour in calculation time with changing 'degauss' value of 'cold' smearing

"I conducted a convergence test for the degauss value in Quantum Espresso input with smearing = 'cold'. The results, ...
Joyal sunny's user avatar
1 vote
0 answers
63 views

Can I use the convergence test results of ecutwfc, ecutrho, and k points obtained from a 2x2 graphene supercell for a larger graphene supercell?

Recently, I conducted convergence tests (ecutwfc, ecutrho, and k points) for a 2x2 graphene supercell, yielding results of 120 Ry, 300 Ry, and 10x10x1 respectively. (Here, we considered convergence ...
Thejan Hasaranga's user avatar
5 votes
1 answer
65 views

How to determine energy convergence threshold and force convergence threshold in Quantum Espresso

In the computational investigation of $MoS_2$ monolayer for its catalytic activity in the hydrogen evolution reaction, how are parameters such as forc_conv_thr and <...
Joyal sunny's user avatar
6 votes
1 answer
521 views

Understanding algorithm of Quantum ESPRESSO from scratch

As someone new to this field, what are some effective strategies or resources I can utilize to study and understand the Quantum ESPRESSO algorithm from scratch?
Joyal sunny's user avatar
5 votes
0 answers
22 views

How to construct a reasonable model of yellow phase FAPbI3 used for DFT calculation from experimental results?

I construct an initial model of yellow phase FAPbI3 from literature. After I viewed this structure using VESTA, it had so much duplicated H, N and C atoms. I know that I need to delete some atoms to ...
Tieyuan Bian's user avatar
3 votes
1 answer
76 views

At a particular K-point (Monkhorst Pack) grid, SCF calculation is not converging

During a convergence test of (MoS2 2x2x1) monolayer using Quantum ESPRESSO, I tried several K-point Monkhorst-Pack grids. According to my understanding, the calculation time and computational cost ...
Joyal sunny's user avatar
3 votes
0 answers
33 views

Energy corrections to be added in my DFT input of Quantum ESPRESSO for studying catalytic activity of MoS2 for hydrogen evolution reaction

While investigating 'catalytic activity of MoS2 (monolayer) in hydrogen evolution reaction', what are the energy corrections that I am supposed to add in the DFT input (using Quantum ESPRESSO) to get ...
Joyal sunny's user avatar
7 votes
1 answer
184 views

Convergence testing in DFT calculation

I have done convergence testing for MoS2 (2x2x1) monolayer structure in the following order: ecutwfc ecutrho k_points After setting these values, I would like to include vdW correction to the system ...
Joyal sunny's user avatar
5 votes
0 answers
35 views

What is best way to get lowest adsorption site at subsurface of high entropy alloys?

I am currently studying diffusion of oxygen in high entropy alloys. I want to calculate the activation energy from an adsorption site on the surface to the subsurface. I placed the oxygen atom below ...
Nana Kofi Boakye's user avatar
3 votes
0 answers
43 views

convergence not achieved after 80 iterations [closed]

I am trying to run a scf calculations to obtain the band structure. However, in the output file, it is show that the convergence is not achieved after 80 iterations. ...
Roman Punk's user avatar
4 votes
1 answer
38 views

Siesta - Segmentation fault error

I am trying to perform a scattering region calculation but I get this error : (from .err file) ...
Youssef Chlikhy's user avatar
3 votes
1 answer
66 views

Is there a minimum inter-defect distance when introducing point defects into a 2D structure, ensuring defects don't exhibit significant interactions?

I am currently conducting a DFT investigation into the magnetism of 2D materials by introducing defects into the structure. Is there a minimum distance I should maintain between two defects in ...
Thejan Hasaranga's user avatar
6 votes
0 answers
59 views

Why are some pseudopotentials not readable in Quantum Espresso?

I am using the pseudopotentials generated using "atomic" code by A. Dal Corso after downloading the pslibrary.0.3.1. ...
Misbah 's user avatar
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8 votes
1 answer
368 views

How to choose hybrid pseudopotentials in Quantum ESPRESSO?

I am trying to perform DFT calculations on lead halide perovskite system using Quantum Espresso However, I am confused in choosing the pseudopotentials. The hybrid pseudopotentials are recommended to ...
Misbah 's user avatar
  • 183
6 votes
2 answers
222 views

Are there scripts available for AIMD?

I need to determine which of two electrolyte is the best for a hydrogen fuel cell. As far as I understand, the first thing to do is to compute their ionic diffusion coefficient and to compare (the ...
Mjf T's user avatar
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5 votes
0 answers
37 views

How to determine the unit cell in heterostructure?

I’ve to create a heterostructure from two monolayers, for example, two graphene sheets or two metal layers. And then I want to rotate the first layer relative to another one by some angle. The ...
Victor's user avatar
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9 votes
3 answers
106 views

Which expectation values can be determined with KS orbitals?

Suppose $A$ is some hermitian operator and $\Psi$ is a many body state function of a many-body hamiltonian $H = T + U + V$, where $U$ is electron-electron interaction and V is electron-nuclear ...
Mikke Mus's user avatar
  • 253
2 votes
0 answers
34 views

How to choose k grid using pymatgen for VASP?

Before I start; sorry for this lengthy question. I am confused about choosing the correct set of K points for the K-convergence test for VASP calculations. The system of my interest has an ...
Nilabja Kanti Sarkar's user avatar
5 votes
0 answers
163 views

Help regarding Geometry Optimization of a bimetallic surface

I am trying to perform a geometry optimization (GEO_OPT) of a FCC 111 Pt$_{0.5}$Au$_{0.5}$ bimetallic surface (10x10x3) generated from ASE, with a lattice parameter of 3.9 $\overset{\circ}{\mathrm{A}}$...
ARKA PRAVA SARKAR's user avatar
4 votes
1 answer
115 views

Convergence not completed in scf for bands

I want to calculate scf for bands calculation. Before I can proceed, I face an error of convergence: ...
Roman Punk's user avatar
2 votes
0 answers
38 views

Error in Quantum Espresso: cannot read atomic specie from: ATOMIC_POSITIONS {crystal}

Can you kindly help me understand the following type of error I get while calculating scf for bands? ...
Roman Punk's user avatar
4 votes
1 answer
164 views

Density of states does not scale properly with supercell

I am performing some DFT calculations of monolayer hexagonal boron nitride in Quantum ESPRESSO. I have been trying to calculate the density of states of a 7 x 7 supercell of h-BN, but the resulting ...
TheSimulator's user avatar
1 vote
0 answers
18 views

Thermal Conductance along the lateral and longitudinal direction

Suppose the left and right leads are both copper rod and the central scattering region is one monolayer graphene sheet. There is no chemical bonding formed between Cu and C atoms. The copper and ...
Kieran's user avatar
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4 votes
1 answer
79 views

Thermal vs dynamical stability

Dynamical stability is checked by a phonon curve. Thermal stability is checked by a molecular dynamics simulation. What is the difference between them?
ArduinoEnthusiast's user avatar
3 votes
0 answers
52 views

BoltzTraP : getting the error 'segmentation fault'

I am doing some calculations with Quantum Espresso and wanted to calculate the electronic conductivity of my 2D nanosheet using BoltzTrap. After the successful creation of the BoltzTraP.def and the ...
Youssef Chlikhy's user avatar
3 votes
1 answer
46 views

Help regarding SLME calculation

Information Paper - https://www.sciencedirect.com/science/article/abs/pii/S1566119918302787 Github Link - https://github.com/ldwillia/SL3ME Question - I have been studying solar cell materials. I ...
epsilon02fft's user avatar
  • 1,502
4 votes
1 answer
64 views

How can I solve the error in TRANSIESTA calculations? [duplicate]

Recently, I've been trying to calculate the transmission coefficients for the molecular junction (Au lattice - molecule - Au lattice) using SIESTA, TRANSIESTA, and TBtrans. As you know, the procedure ...
Jonghwan Lee's user avatar
3 votes
0 answers
32 views

Relax calculation not converging

I am using a DFT+U+V approach and using a pseudohybrid density functional for extended Hubbard Coulomb interactions along with GBRV ultrasoft pseudopotentials (PBEsol). This enables me to open a gap ...
Austin's user avatar
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3 votes
0 answers
41 views

How to calculate band gap alignment for different layers used in double perovskite solar cell?

I want to compare the electronic bands (VBM and CBM) of a double perovskite material with other layer using like transports both holes and electrons .I tried to calculate them, but the values I ...
KAMAL ASSIOUAN's user avatar
3 votes
0 answers
9 views

How to build input files to obtain vibrational and thermodynamic measurements using Quntum Espresso?

I'm working with a SiPOCa structure and I've already done the SCF, NSCF, DOS, BANDS, CHARGE DENSITY, FTIR and RAMAN calculations. Now I would like to calculate the vibrational and thermodynamic ...
Caroline Santos 's user avatar
2 votes
0 answers
13 views

Error in the PH file for RAMAN and FTIR calculation

I am doing the Raman and FTIR calculations using quantum espresso, I ran the following codes ...
Caroline Santos 's user avatar
4 votes
0 answers
41 views

vc-relax calculation not converging with some pseudopotentials

I am new to Quantum ESPRESSO and it's my first calculations with $\mathrm{CsPbBr}_3$ perovskite structure. I am trying to perform vc-relax calculations. The ...
Misbah 's user avatar
  • 183
4 votes
1 answer
55 views

Is it neccessary to apply dipole corrections in TMD bilayers?

I am at the beginning of my PhD and I just learned about the dipole correction in ab-initio calculations. I have seen that it is used mainly when an electric field is applied to a system. But I have ...
Miguel Morales Cocera's user avatar
3 votes
0 answers
19 views

How to construct the input files to obtain the structural measurements using Quntum Espresso?

I'm working with a SiPOCa structure and I've already done the SCF, NSCF, DOS, BANDS, CHARGE DENSITY, FTIR and RAMAN calculations. Now I would like to calculate the structural measurements of this ...
Caroline Santos 's user avatar
6 votes
1 answer
251 views

Formation Energy Calculations

How may I calculate each term of the formation energy equation using DFT? I am assuming that for every software (i.e. Quantum ESPRESSO; Wien2k), the calculation procedure must be the same.
epsilon02fft's user avatar
  • 1,502
6 votes
1 answer
79 views

Creating a Hypothetical Hexagonal Monolayer Structure Similar to MoS2

I am seeking guidance on how to generate a POSCAR file for a hypothetical monolayer with a hexagonal structure similar to MoS2. Can anyone provide me with a step-by-step procedure or recommend any ...
Farah Shehzadi's user avatar
4 votes
1 answer
40 views

Simple Quantum Espresso-Phonon

I am completely new to material modelling. I am trying to calculate phonon frequency at X point for Aluminium fcc. I picked an fcc lattice and displaced the atoms at x=0 by (+0.1) and those in x=0.5 ...
PyronGr's user avatar
  • 41
4 votes
1 answer
76 views

Help with Geometry Optimization in CASTEP

I am a beginner in CASTEP simulation and I need some guidance on the general steps for geometry optimization. I have tried the following three approaches: (1) Build unit cell > geometry ...
Minhaz Mahmood's user avatar
2 votes
0 answers
54 views

Prerelaxation before AIMD with VASP

I am investigating a bulk structure by ab initio molecular dynamics (AIMD) implemented in VASP. I was wondering, how to choose the initial geometry (= POSCAR file) to run the AIMD simulation. In the ...
Lukas's user avatar
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