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Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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Which occupation and potential should I prefer during the input preparation for Semiconductors (Quantum Espresso)?

I am trying to calculate second order force constants for GaAs (preparing input file for ShengBTE). I successfully ran pw.x, but after that when I ran ph.x, I got the following error. ask # 0 from ...
Muhammad Hasan's user avatar
1 vote
0 answers
22 views

Is it necessary to include non-analytical correction in the phonon calculations for intrinsically dipoled monolayers?

Good day, Is it necessary to include non-analytical correction (using Born effective charges and dielectric constants tensors) in the phonon calculations for 2D materials that is intrinsically dipolar ...
UCU110's user avatar
  • 141
3 votes
1 answer
34 views

ERROR in NSCF calculation execution in QE

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Thejan Hasaranga's user avatar
3 votes
0 answers
27 views

How to calculate Zero Point Energy of an adsorbed molecule on a surface with quantum espresso?

I want to calculate zero point energy of a molecule that is adsorbed to a surface (by fixing the surface) with help of quantum espresso? I want a detailed explanation. I am not asking about the modes ...
SOURAV GHOSH's user avatar
6 votes
1 answer
42 views

Reference energy for bands

When DFT band structure is obtained, how do we know whether it is calculated with respect to vacuum level or any other? I heard that these band structures can be calculated w.r.t. vacuum level where ...
AbPhys's user avatar
  • 801
1 vote
0 answers
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How to efficiently calculate Hubbard parameters using hp.x for isolated dopant?

Background I know how to use hp.x in case of undoped periodic system. We take a small unit cell, apply some initial guess values to obtain the ground state (pw.x), and then run the hp.x on top of it ...
Abdul Muhaymin -Free Palestine's user avatar
4 votes
0 answers
38 views

Spin-orbit coupling(SOC) in geometry optimisation

When I tried including SOC during the optimization of InBi lattice constants, the lattice constant increased from 4.6 Å (without SOC) to more than 6 Å (with SOC), which seems like an 'incorrect' ...
James's user avatar
  • 95
2 votes
0 answers
41 views

Mean square displacement (MSD) graph from AIMD simulation

To get the slope from MSD graph, how to do the fitting if the graph is not perfectly linear? Do we need to do fitting only in the linear region?
SRJ's user avatar
  • 21
4 votes
0 answers
29 views

Consequences of starting a new relaxation calculation from the final coordinates of an interrupted run

In order to address oscillating total force during an ongoing relaxation calculation in Quantum ESPRESSO, I've found it effective to interrupt the current run and commence a new relaxation calculation ...
Joyal sunny's user avatar
3 votes
1 answer
37 views

Gate voltage on a quantum dot device, including the electrodes

I am trying to simulate the effect of a gate voltage on a quantum dot device, including the electrodes. To do so, I am using the method described in the article "Manipulating the voltage drop in ...
Mohamed Amine's user avatar
3 votes
1 answer
44 views

Why is the SCF calculation performed after VC-RELAX more energetically stable than the VC-RELAX calculation in QE

Recently, I performed a vc-relax calculation in QE. After vc-relax, I performed an scf calculation, including all the optimized parameters from the vc-relax output file (cell parameters, atomic ...
Thejan Hasaranga's user avatar
4 votes
1 answer
59 views

Why do certain atoms remain fixed during relaxation?

I am running PBE defect calculations on InAs in Quantum Espresso. Whenever I run relax, the first 8 atoms stay fixed in place, while the rest displace by some amount. For example, ...
Austin's user avatar
  • 101
6 votes
1 answer
140 views

What's the temperature of the output electronic properties get from Quantum Espresso/VASP, even if we use 298 K cell info (atom position) as an input?

Normally to prepare input file (structure of materials) for Quantum Espresso/VASP, I searched the corresponding CIF file from this website (http://www.crystallography.net/cod/result.php), after that I ...
Muhammad Hasan's user avatar
2 votes
0 answers
19 views

Investigation of ferro, ferri, antiferro, para and dia magnetism using QE

Can Quantum ESPRESSO be used to investigate ferromagnetism, ferrimagnetism, antiferromagnetism, diamagnetism, and paramagnetism? If so, could you please elaborate on how these types of magnetism are ...
Thejan Hasaranga's user avatar
4 votes
0 answers
32 views
+50

Extracting and Analyzing eg and t2g Orbitals' Contributions from VASP DOS Calculations

I need assistance with extracting and analyzing the egeg​ and t2gt2g​ orbitals' contributions from my VASP DOS calculations. I have performed the necessary calculations and obtained the DOSCAR and ...
Farah Shehzadi's user avatar
2 votes
1 answer
35 views

Finding Octahedral and Tetrahedral sites

I am very new to material research. I am trying to find the xyz coordinates of all tetrahedral and octahedral sites of Pd (110) plane. I will be grateful if you could point out the xyz coordinates ...
user10238's user avatar
3 votes
0 answers
21 views

How can one output GPAW energy densities after a SCF calculation?

I'm looking to obtain the final energy densities in real space of the terms that compose the total energy in GPAW: $$E = E_{kin} + E_{coul} + E_{xc} + E_{zero}$$ I can get the ...
rbw's user avatar
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3 votes
0 answers
18 views

Spontaneous Polarization on a n-doped system ( ABO3 perovskite ) in VASP

I am trying to perform a spontaneous polarization calculation on a n-doped ABO3 system using the berry phase approach in VASP. I use a 3x3x3 supercell and I am trying to follow the same way we ...
Darin Joseph's user avatar
3 votes
0 answers
19 views

Result of FTIR and RAMAN calculations for SiPOCa structure

Using Quantum Espresso models this structure with the following input files. However, the ph.x IR column always shows zero. Does anyone know why this result? ph.x input: ...
Caroline Santos 's user avatar
2 votes
0 answers
33 views

static self-consistent calculations

How is the static self-consistent calculations different from standard self consistent field calculations? Please also explain this in context of other type of calculations e.g. single shot.
AbPhys's user avatar
  • 801
5 votes
1 answer
215 views

Calculating structural stability of a doped plane

The following image indicates an equation published on a reserach paper which was used to calculate structural stability in a metal atom-substituted graphene sheet. Can anyone tell me if we should ...
Thejan Hasaranga's user avatar
4 votes
0 answers
34 views

Time efficient way of conducting vc relax calculations while mainting accurate results at the same time

I believe this VC-relaxation calculation will take a significant amount of time to successfully complete. Referring to the literature (which indicates that the vanadium substitution atom is positioned ...
Thejan Hasaranga's user avatar
1 vote
0 answers
35 views

Formation and Optimization of Dimers, Trimers, Tetramers, and Beyond

What is the procedure to follow in order to computationally create clusters such as dimers, trimers, or tetramers using Quantum ESPRESSO?
Thejan Hasaranga's user avatar
3 votes
0 answers
24 views

Examples of low sensitivity of observable behavior to the choice of DFT functional

This question is the antipode to another one I just asked. Here I am looking for examples where not immediately obvious properties are predicted well by a range of functionals or pairs of rather ...
Andrey Poletayev's user avatar
6 votes
0 answers
57 views

Examples of high sensitivity of observable behavior to the choice of DFT functional

Most computational materials science studies perform or reference some sort of baseline process for choosing the DFT functional that they will employ to model their system. It is unlikely that a ...
Andrey Poletayev's user avatar
2 votes
0 answers
37 views

Stiffness constants C11

How can I accurately extract and reproduce the values of $C_{11}$ for 2D hexagonal structures with two independent in-plane constants $C_{11}$ and $C_{12}$? I've used Vaspkit to extract a value of ...
Hamza Bekk's user avatar
7 votes
1 answer
90 views

Does the size of atoms influence the speed of DFT calculations when comparing systems with almost the same number of atoms

How does the size of atoms within a structure influence the speed of DFT (Density Functional Theory) calculations? considering that the calculation speed is known to scale cubically with the number of ...
Joyal sunny's user avatar
7 votes
0 answers
74 views

Correct method for structure optimization using DFT tools

Lets's say I want to start off DFT calculations for a material whose experimental cell constants are known. So I have two ways to get the correct structure to later on calculate, say, band structure ...
AbPhys's user avatar
  • 801
5 votes
0 answers
51 views

Exploring the Impact of Transition Metal Doping Percentage on Hydrogen Evolution Reaction Catalysis in Transition Metal Dichalcogenides using DFT

Transition metal dichalcogenides (TMDCs) are extensively researched for their efficiency as catalysts in the hydrogen evolution reaction (HER). I aim to employ Density Functional Theory (DFT) to ...
Joyal sunny's user avatar
4 votes
0 answers
21 views

Identifying non-relativistic, scalar relativsitic and full relativistic POTCAR

How to identify if the given VASP POTCAR pseudopotential is non-relativistic, scalar relativistic or fully relativistic from the content of the file? For example, I found EATOM values in relativistic ...
AbPhys's user avatar
  • 801
6 votes
1 answer
41 views

Has anyone used Critic2 with Quantum ESPRESSO? Need help to determine non-nuclear charge determination

I have installed Critic2. Need to know how to determine interstitial site locations of a structure and their charges in those sites (in non nuclear maxima sites). I have calculated 3D charge densities ...
Sak's user avatar
  • 981
4 votes
0 answers
30 views

How to calculate the volume energy loss function (VELF) using Quantum ESPRESSO?

How to calculate the volume energy loss function (VELF)? Could you please share with a simple example (with related input files, output files and/or plot)? Any relevant links would also be welcome.
Sak's user avatar
  • 981
3 votes
1 answer
39 views

Quantum ESPRESSO: how to calculate mobility?

How to calculate the mobility? Could you please share with a simple example (or simpler equation) to do this? Or in other words, if we have $E_g$, $E_F$, $P$, $V_{cell}$, $E_{vb,max}$, $E_{vb,min}$, $\...
Sak's user avatar
  • 981
2 votes
0 answers
32 views

Methods of convergence in GW-BSE calculations: Quantum ESPRESSO and BerkleyGW

I have been learning BSE calculation through Quantum ESPRESSO and BerkeleyGW. I have been successful to obtain the silicon optical spectra (via GW-BSE), as instructed in the tutorial. The values of ...
Sak's user avatar
  • 981
4 votes
1 answer
71 views

How to plot absorbance from a Quantum ESPRESSO optical calculation using ε1, ε2, and energy data?

I have a calculation via DFT-RPA, which calculates epsilon_2 and energy (eV). For optical property calculation, we usually plot epsilon_2 vs energy (eV). However, I need to know to convert the y-axis ...
Sak's user avatar
  • 981
6 votes
1 answer
167 views

Elastic property in Voigt, Reuss and Hill approximations

DFT tools e.g. vaspkit after post-processing elastic calculation results provide elastic properties, say, bulk modulus for bulk single crystal and bulk polycrystal. Bulk single crystal values are ...
AbPhys's user avatar
  • 801
7 votes
1 answer
169 views

Significant external pressure in non-SCF calculation results

I performed full structure optimisation (positions, cell volume and cell shape) using 15x15x3 k-mesh in VASP and safely assumed that the structure is reasonably relaxed as the external pressure found ~...
AbPhys's user avatar
  • 801
5 votes
1 answer
115 views

problem calculating formation energy per atom using vasp

Using the below code I am trying to calculate the formation energy per atom and bandgap given the cif file. the values that are present in the material project. but I got these values which are wrong ...
harsh's user avatar
  • 223
4 votes
0 answers
49 views

May I change the ICntrl variable in Gaussian 16?

Ive been trying to do energy calculations under the influence of a perturbative field with the BLYP and B3LYP functionals. Using the following input files: BLYP: ...
Atom's user avatar
  • 1,005
8 votes
2 answers
108 views

How do DFT software packages enforce spin multiplicity?

New to matter modeling In KS-DFT software packages (I particularly have Gaussian in mind although I know they are ultimately not open-source), how is finding a ground state with a certain spin ...
greatscissors's user avatar
1 vote
0 answers
21 views

Optimization error in quantum dot graphene doping with antimony atoms

...
fatemeh's user avatar
  • 11
6 votes
1 answer
60 views

How to perform LC-BLYP calculation with GAMESS?

I am currently working on time-dependent density functional theory (TDDFT) calculations for both singlet and triplet states using the LC-BLYP functional in GAMESS. I believe I have correctly followed ...
Alireza Lashkaripour's user avatar
5 votes
1 answer
74 views

Can conventional unit cell have higher symmetry than primitive cell for the same crystal?

This question arises from the last sentence of the first paragraph (see here) of the section "Formalism". If primitive cell can have lower symmetry, why don't the DFT results using these two ...
AbPhys's user avatar
  • 801
2 votes
1 answer
84 views

Can lattice vectors have negative components for DFT calculations?

I am using VASP for DFT calculation where the lattice vectors of POSCAR file for the hexagonal system are as follows. This I generated using VESTA ...
Nilabja Kanti Sarkar's user avatar
4 votes
1 answer
166 views

Transiesta, not converging with semi-conductor electrodes

Hello transiesta users. I am trying to calculate the I-V curves of 2D blue phosphorene(electrodes are made of the same material the semiconductor 2D blue phosphorene ) by using transiesta code. First ...
naima ennassiri's user avatar
12 votes
1 answer
134 views

Which data files need to be stored after publishing a DFT study?

When we browse literature on first-principle study, we see they usually report the methodology, used program with the version number and the results. In some cases, people share their input files, ...
Abdul Muhaymin -Free Palestine's user avatar
6 votes
1 answer
88 views

Should alat value be used as it is in calculation or multiplied with CELL_PARAMETERS value?

I am trying to perform DFT calculations for CsPbBr3 system on QE v7.2. To exploit symmetry i have given the space_group=221 and ...
Misbah 's user avatar
  • 293
5 votes
0 answers
38 views

About alignment of 2D monolayer band structures

I need to do the alignment of band structures of one 2D monolayer. I have created some vacancies in the 2D monolayer using VASP and calculated the band gap values (GGA) corresponding to different ...
Poonam Sharma's user avatar
2 votes
0 answers
32 views

How to rotate Octahdrals locally along with unit cell axis

As the continuation of this discussion d orbitals PDOS analysis, I am curious about crystal field effects on a given atom by analysing $m_l$ projected DOS, the individual d-orbitals are given with ...
Kratos1611's user avatar
4 votes
1 answer
101 views

Energies from single points vs. AIMD for training Machine Learning Force Fields

I am currently training a force field using machine learning techniques. One way to test the performance of the ML model is to use the force field for a production run (= molecular dynamics) and ...
Lukas's user avatar
  • 303

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