Questions tagged [density-functional-theory]
For questions about simulations using Density Functional Theory.
439
questions
10
votes
4answers
314 views
Are dispersion correction methods for DFT (such as D3) useful for geometry optimization?
For what I know the DFT-D3 method or similar corrections that take into account dispersion effect, add this type of contribution through calculation of atom pairwise interactions at the end of an ...
10
votes
3answers
485 views
Which DFT functional should I use to simulate spectra of pesticides?
I am mainly searching for functionals to calculate spectra of pesticides. I found the benchmark test from Goerigk and Grimme$^1$, but don't understand which of the functionals suits my purpose the ...
7
votes
2answers
99 views
Why is there a large discrepancy between calculated frequency dependent dielectric function and experimental measurement?
I am calculating the frequency dependent dielectric function of $\ce{SiC}$ using VASP. After a geometry optimization, the INCAR file below is used for the ...
4
votes
0answers
33 views
How to do a Sampling on the boundary of Brillouin zone in VASP
I use VASP to do my DFT calculation. I have to do a self consistent calculation to generate my CHGCAR. I want to ask is there anyway to write the KPOINTS file to generate K-meshing grid which can ...
5
votes
0answers
27 views
Is it possible to install thermo_pw on windows 10?
For research purpose, my team needs to use thermo_pw package for ab-initio simulations. But the issue we are running into is that we cannot find a way to install it on our computer. We are using ...
11
votes
2answers
325 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.
9
votes
1answer
65 views
Why VASP calculates the elastic constant for another trigonal space group?
Please, help me to understand the problem. I calculated the elastic constants for the beta PHB (Space group P3221 (154)), it has to show the reduced elastic constant matrix (six), however, ...
11
votes
1answer
46 views
What does this temperature & total free energy profile mean (obtained from VASP NVT molecular dynamics simulations)?
In order to obtain molecular dynamics (MD) simulations trajectory for computing phonon dispersion relation at finite temperature, I performed NVT MD simulation using VASP for my target system.
Here is ...
4
votes
1answer
44 views
Optical anisotropy from first-principles
I am interested in the theoretical study of optical anisotropy (birefringence, dichroism etc.) of different materials. I have seen DFT works studying optical anisotropy from the calculation of ...
7
votes
1answer
36 views
How to determine the more stable configuration between a flat and a buckled monolayer with DFT?
Using first principles methods (quantum espresso code) I would like to find if a monolayer of a material is flat or buckled. Using the van der Waals interaction in the calculation I found that the ...
6
votes
1answer
38 views
How to make this DOS plot more smooth and add more points around Fermi level?
I have calculated and plotted the DOS for a doped monolayer 3x3x1 supercell. I want to make the plot more smooth and add more points around Fermi level.
Knowing that these are my settings for the ...
8
votes
1answer
39 views
When import volumetric data (spin density of CHGCAR) to VESTA which option should we pick here?
I am trying to plot SPIN DENSITY isosurfaces using VESTA. I have used vaspkit option 312 to create ...
8
votes
1answer
61 views
What is the meaning of element-rich environment in calculating formation energy?
I want to use the formation energy formula used by the article in the picture below. The authors have used the term S or Sn-rich environment. What is the meaning of ...
16
votes
2answers
3k views
Solving the Schrödinger equation as a service?
Does anyone know of a company with a cloud-based service which takes some representation of a molecule as an input, and then somehow solves the Schrödinger equation to some level of accuracy and ...
8
votes
2answers
308 views
Pressure applied DFT calculations in Quantum ESPRESSO
I am trying to perform the pressure-induced DFT calculations in Quantum ESPRESSO. For this, I have calculated the lattice constant of the cubic structure by vc-relax...
8
votes
2answers
149 views
Data format of wannier90_hr.dat from wannier90
I did a calculation on a bulk system with DFT and fit it with the tight binding matrix with wannier90. There is question on this. I try to write my own code to construct a slab tight binding matrix ...
5
votes
2answers
315 views
What is the meaning of these d states names?
I have read in the article at the reference below that :
the Mn substitution leads to localized states (impurity bands) within the band gap. The Mn 3d orbitals split into a single a$_1$ (d$_{z^2}$) ...
9
votes
1answer
52 views
Are electron dipolar spin-spin interactions included in DFT calculations?
I am studying point defects in hBN using Quantum ESPRESSO. It is not clear if electron spin-spin interactions are typically/can be included in DFT calculations. I understand that spin-orbit ...
10
votes
2answers
353 views
How can we say that the KS equation is describing a noninteracting many-electron system?
Based on HK's two theorems, the density functional theory was built. Because one can't find the universal energy functional $F_{HK}[n(r)]$, Kohn and Sham further proposed the Kohn-Sham ansatz: mapping ...
6
votes
0answers
43 views
How can I calculate the J value in an antiferromagnetic material?
I am new to DFT, especially in doing DFT for magnetic materials. I recently came across this paper which indicated the calculation of the J value in the case of antiferromagentic materials as per the ...
7
votes
1answer
56 views
PES of Tetramethylthiuramdisulfid / Problem with Disulfidbridge
I like to perform a DFT Study on Tetramethylthiuramdisulfid. So I made a structure optimization for my start structur with PW6B95D3/aug-cc-pvtz to get a good structure to begin my dihedral scan to get ...
10
votes
1answer
115 views
DFT xc integration grid for periodic boundary conditions
I am writing my own DFT code using Gaussian basis and now I am writing the periodic boundary conditions (PBC).
What integration grid people usually use for Gaussian basis PBC (+ reference please)?
For ...
7
votes
0answers
39 views
Is it possible to construct a tight binding matrix of high atomic layer thin film from the lower one?
Give a tight binding matrix of a few atomic layer thin film system, is it possible to construct a tight binding matrix of higher atomic layers thin film from the lower one? For example, I have a 4 ...
4
votes
1answer
101 views
How to interpret spin density isosurface figures?
The figure below shows the spin density isosurfaces of 3x3x1 ScS2 monolayer supercell doped with Mn atoms. This figure was generated using VASPKIT and ...
6
votes
1answer
38 views
What is the meaning of EATOM tag in the POTCAR files of VASP?
I am wondering what is the meaning of EATOM tag in the POTCAR files of VASP. What is its relationship with the energy of an ...
7
votes
0answers
41 views
Single electron transfer periodic DFT in VASP
I have the following question: I am currently studying the electrocatalytic CO2RR on Cu materials using periodic DFT calculations and I am using the CHE model to describe the proton electron transfer ...
5
votes
1answer
53 views
Divergence behaviour of surface energy
By definition, the surface energy of a thin film or a slab model is defined as
$$
\sigma = \frac{1}{2A}(E_{slab} - N\cdot E_{bulk})
$$
where $N$ is the number of atoms in the thin film and $E_{bulk}$ ...
6
votes
1answer
67 views
“A dense k mesh of 40,000 k points was used in the Brillouin zone”. How is this number obtained?
In publications, I usually see the statement "A dense k-mesh of 40,000 k-points was used in the Brillouin zone". An example of this is in this paper. But in the paper they have ...
11
votes
1answer
86 views
What does a density of states (DOS) plot show?
I have plotted the density of states using GGA-PBE exchange correlation functional for magnesium silcide but I really do not know what the equations involved are in this process, and how they relate ...
6
votes
1answer
38 views
Where are the atoms located in a charge density calculation using DFT?
The charge density (electron distribution) is calculated self-consistently by employing DFT, so a question arises here: where are the atoms located, or are their positions fixed?
8
votes
2answers
300 views
What is the maximum allowed doping concentration?
Let's consider an example of a 3x3x1 supercell of WS2 monolayer which has 9 W atoms. If we substitute two of them with 2 dopants, the concentration will be 2/9 ...
7
votes
1answer
58 views
How to calculate E_TM in the formation energy formulas?
I found in the literature that the formation energy of doped supercell (e.g.: 4x4x1 supercell with one dopant atom) has many formulas, and the most common one is :
$...
22
votes
3answers
1k views
Geometry optimization: what happens in the algorithm?
Geometry optimization using density functional theory (DFT) is done by moving the atoms of a molecule to get the most stable structure with the lowest possible ground state energy. My question is what ...
6
votes
1answer
64 views
How to set NCORE, KPAR and NBANDS to speed up calculations on VASP?
I am searching of how to set the tags NCORE, KPAR and NBANDS on a specific systems to speed up calculations. Could you please tell me the rules to follow ?
8
votes
1answer
53 views
How to solve this Bandup software problem?
I have compiled the Bandup software using this command : ./build -compiler gfortran. After that, I tried to follow the tutorial inside the directory ...
5
votes
1answer
38 views
Regarding POSCAR file for bulk Silicon
I am newbie to DFT and I am trying to understand the different input parameters in the VASP POSCAR file of bulk silicon system, provided in the examples here. I am trying to find the lattice constant ...
10
votes
1answer
125 views
How to visualize spin density isosurfaces?
What is the package used for visualization of spin density isosurfaces in VASP like the ones shown below? A simple example/tutorial would be very appreciated.
6
votes
0answers
68 views
Is there a software package to analyse interactions in crystals?
I have been using Quantum ESPRESSO, specifically the pp.x module to
study interactions via charge density plots. The process is slow as
for crystals containing ...
12
votes
1answer
72 views
How to cut properly a slab from a cif file?
I am trying to do DFT calculations on ethanol adsorbed on Pd, both surfaces 111 and 100. I have the cif file from the database and also I have built the new unit ...
6
votes
0answers
36 views
How to interpret WannierTools Python code that generates tight-binding model in the wannier90_hr.dat format?
I am getting myself acquainted with Wannier Tools. Wannier Tools requires two inputs, a wt.in file, and a .dat file. This .dat file should have the structure explained in the manual here. This file ...
5
votes
0answers
32 views
Kinetic energy cut-off for Gaussian-type orbitals when applying periodic boundary conditions
I have a solid with PBC (periodic boundary conditions) and I want to perform a DFT simulation. I use GTO as the basis. In a paper I read, I can transform the GTO to a Bloch function (crystalline ...
8
votes
1answer
51 views
How to calculate the parity of a band at a particular point in Brillouin zone
Some references mentioned that the calculation of $Z_2$ topological invariant of a crystal can be greatly simplified if the crystal contains inversion symmetry. But it involves the calculation of the ...
6
votes
1answer
55 views
How to obtain electron charge density per unit volume about a water molecule using SlowQuant?
@Nike Dattani's answer to How to “get my feet wet” in Density Functional Theory by simulating a water molecule using Python recommends SlowQuant. I've used the install instructions for Linux on my ...
7
votes
1answer
81 views
Band structure calculation
I want to do band structure calculation of Magnesium silicide for GGA in VASP. Can anyone please help how to do this by setting initial ...
7
votes
1answer
55 views
VASP input file for formation energy calculation
I want to calculate the formation energy of $\ce{Mg2Si}$ using VASP. What should be the initial steps to perform this run? What INCAR tags are required? Any help ...
8
votes
1answer
78 views
Regarding spin-orbit coupling on DFT codes
In most DFT codes like QE and VASP, spin-orbit coupling (SOC) can be incorporated by employing fully relativistic pseudopotentials. My question is with regard to the implementation of SOC among ...
4
votes
0answers
30 views
What are the TS, MBD keywords for new (5.4.+) VASP versions?
I tried IVDW = 2202 for MBD as mentioned on the website but I got the following error:
...
9
votes
1answer
138 views
SCAN-RVV10 geometry optimization
I'm using SCAN-RVV10 to optimize the hexagonal-BN but the optimized geometry doesn't look true as the calculated interlayer distance is far smaller than the experimental value(exp=3.35 Aangstrom, calc=...
10
votes
2answers
292 views
How to calculate DFT energy with density from another level of theory?
I need to calculate the DFT energy given the density of another level of theory, for example Hartree Fock.
$E[\rho_{HF}]$
This is sometimes used to fix various electron delocalization errors in ...
8
votes
1answer
45 views
What are the input parameters of VASP for 2D material geometry optimization?
Apparently, my input parameters are not good for geometry relaxation of 2D materials using VASP.
...
