Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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SCAN-RVV10 geometry optimization

I'm using SCAN-RVV10 to optimize hexagonal-BN but optimized geometry not looking true as the calculated interlayer distance is far smaller than the experimental value(exp=3.35, calc=3.20)(SCAN-RVV10 ...
6
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1answer
174 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 ...
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21 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. ...
5
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22 views

What are some examples where TD-DFT was successful and where it fell short in describing photophysical or photochemical processes?

Time-dependent Density Functional Theory has been around for quite a while now, Runge, Erich; Gross, E. K. U. (1984). "Density-Functional Theory for Time-Dependent Systems". Physical Review ...
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1answer
64 views

How to evaluate the exciton velocity?

I have calculated the exciton wave functions using the GW-BSE method: $$\tag{1}|S\rangle = \sum_{cv\mathbf{k}} A_{cv\mathbf{k}} |cv\mathbf{k}\rangle$$ where $c$ for conduction and $v$ for valence ...
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Effect of temperature on density of states effective mass

The experimental study shows that Density of state effective mass is calculated at 300K while in theoretical study DFT yield Density of state effective mass at 0K .Why there is so much temperature ...
5
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1answer
68 views

VASP error when trying to do calculations in the presence of an electric field

I am trying to observe the effect of the electric field on 2D materials. I applied electric field by introducing three tags: ...
6
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2answers
174 views

How to perform band-structure unfolding in VASP?

I have created a band structure for 3x3x1 doped-supercell using VASP, and I obtained the figure below. Now I want to do band-unfolding. What are the simplest ways ...
12
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2answers
102 views

Procedure to classify errors in Kohn-Sham DFT

I was reading this paper which basically outlines the two main types of errors that one encounters in Kohn-Sham DFT : Density-based errors and Functional-based errors. I understand the practical ...
12
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2answers
478 views

Total energy from KS-DFT: How reliable is it and why?

As the title suggests, my question is fundamental - How reliable are the total energy values from Kohn-Sham Density Functional Theory, and why. I acknowledge that absolute values of energies are ...
9
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1answer
102 views

How to calculate the formation energy of a monolayer using VASP?

I want to calculate the formation energy of WS2 monolayer unit cell using VASP. I am wandering if you could show me the detailed ...
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60 views

How to fix gauge in Quantum Espresso?

I am trying to use Quantum Espresso to manually calculate the Berry phase using the Berry connection, due to evolution along a closed loop in k-space. I want to do this manually instead of using ...
6
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1answer
55 views

Calculating the surface state with Wannier tools

Currently I met a problem when I calculate the surface state of a topologically non-trivial thin film system. I did a DFT calculation and fit the result with wannier function. The fitting looks pretty ...
6
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50 views

Two-stage unbinding & binding energies with DFT

I'm trying to calculate the stability of the product of a coordinate bonding process of molecules A and B in the polarizable continuum solvent model (PCM, solvent set to water). I'm getting energies ...
10
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1answer
64 views

Can I do a “constrained” geometry optimization in Quantum ESPRESSO, such that certain dopants appear in certain positions even after relaxation?

I am studying the magnetic properties of bulk ZnO, so I am doping it with transition metal elements in order to observe the magnetic spectrum. I replace a Zn atom with a transition metal element at ...
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In VASP, which option is better for monolayer relaxation: ISIF=3 or ISIF=4?

Since I have started working on monolayers I was using the ISIF=3 tag for relaxation, this was after recompiling VASP with the modified "...
5
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2answers
80 views

Bash script to extract lattice parameters from CONTCAR

I am using VASP to calculate material properties. I want to know how to extract the lattice parameters from my cells automatically with a script. I know about the method with VESTA (described here How ...
4
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How can I calculate and plot the Molecular orbitals (MO's) from the Gaussian wavefunction file?

This a follow-up question to my previous question. And as per the answer one could create M.O orbitals from the primitives. As a new user of Gaussian, is there any method (or algorithm) to followed so ...
8
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1answer
81 views

What is the source of error in this mBJ-LDA calculation?

I am trying to do MBJLDA calculation for bandstructure for WS2 monolayer unit cell using VASP and following the method provided here : Band Structure mBJ-LDA using Vasp, but I am getting an error ...
10
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2answers
98 views

k-points value in KPOINTS file for the VASP band calculation

I'm a new VASP user, especially for the band structure calculations. I see that KPOINTS files are different for the GO/SP calculations and band calculations. For example in here it shows KPOINTS file ...
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36 views

Troubleshooting mechanistic calculation: Transition state energy and intermediate energy too close

I'm studying a mechanism of aromatic substitution of fluorine which proceeds via an intermediate. I'm searching for transition state using relaxed surface scan, then I optimize the TS and perform IRC (...
6
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2answers
44 views

Does SOC band structure calculations require higher number of k-grids?

In so many papers I see that they carry out soc band structure calculations with much higher kgrid than used for the geometry optimization. Whats the logic behind that?
10
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1answer
70 views

Is Wannier 90 computationally expensive to run?

I'm extremely new to the Wannier90 code. I was planning to install it on a workstation I have but I would be using the cores to run calculations using Quantum ESPRESSO. I have a few quad core i5 PC's. ...
7
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1answer
105 views

How to study a new material without any experimental data about it?

My question is a little bit general. I want to study a 2D monolayer material which hasn't any experimental data available, just some first principles DFT works using PBE, LDA and HSE06 (for band ...
5
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1answer
88 views

Dispersion correction and band structure

Let's say I optimized geometry with PBE+D3. I want to carry out band structure calculation with HSE06, should I add the dispersion correction to the band structure calculation or not? I tried both and ...
3
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2answers
89 views

Energy per unit cell in NWChem differs for different supercells despite the same k-points density

I try to compute the unit cell energy of the $\ce{Ti2CO2}$ MXene with NWchem. Computing the 1x1 supercell with 4x4x1 K-points grid I got -1875 Ha. Computing the 2x2 supercell with 2x2x1 K-points grid ...
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Handling multiple self-consistent solutions with DFT+U

It is well-established that within the DFT+U framework, one can achieve several self-consistent solutions with greatly varying energies for the same exact magnetic ordering. In 2010, Meredig et al. ...
9
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1answer
239 views

What is the “formula unit surface area”?

Firstly, sorry if this question is too basic for this community but seriously I couldn't find any answer. Does it mean the multiplication of the in-plane lattice constants? For example, lets say ...
6
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1answer
61 views

How to carry out HSE06+SOC band structure calculation using VASP?

I could not find any good source for this type of calculation. I'd be very appreciated if someone who is experienced with that to show it step by step
5
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1answer
78 views

How to calculate the enthalpy of formation?

I am following this paper to calculate the formation enthalpy of MgCu$_2$, in which the formation enthalpy is defined as follows: where $E$(Mg$_x$X$_y$) is the total energy of the compound, and $E$(...
5
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2answers
97 views

Calculation of Redoxpotential with Gaussian

I want to calculate the redox potential for a molecule in water. I found a got tutorial at 1. I tried to understand the example. But I got a problem with the unit at the end. The have an result for ...
5
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1answer
34 views

Are these settings for HSEsol accurate enough?

I have conducted HSEsol relaxation on a monolayer unit cell of 3 atoms using VASP, with the settings below : ...
7
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1answer
76 views

Will there be a difference between GGA and GGA+$U$ for material with Sc element involved?

I have a material that contains the transition metal element Sc [3$d$1], and I want to know your opinions if there will be a difference between GGA and GGA+$U$ calculation. Knowing that the other ...
9
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1answer
89 views

How to perform HSEsol in VASP calculations?

I want to perform HSEsol (PBEsol + HSE06) calculation on a material (monolayer) that doesn't have experimental data available. Could you please tell me how to ...
10
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1answer
176 views

A concern about IRC results

I've run an IRC (intrinsic reaction coordinates) calculation from my TS (transition state) and got two minima for each side. I am concerned about them. One of them took about 100 steps to be achieved ...
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17 views

Is it possible to calculate the variation of magnetization M(T) for a diluted magnetic semiconductor?

Please if you can help me with some resources and tutorials. Is there any simulation program (for example a DFT package) to determine the variation of magnetization M(T) for diluted magnetic ...
9
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2answers
85 views

Can we consider SOC in FM materials using QE?

This is a follow-up question to my question posted here. I've been trying to study the effects of spin-orbit coupling (SOC) on the band structure of ferromagnetic (FM) material VSe$_{2}$. The input ...
11
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1answer
44 views

How can I properly attach ligands to a surface?

The main aim of my venture is to study the effect of the presence of surface ions on the band structure of Si slab using Quantum ESPRESSO. I've tried to use iQmol to attach ligands to the surface. The ...
5
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1answer
34 views

Fermi level shift downward in the thin film structure

I did a band structure calculation of a thin film structure with different number of atomic layers. I found that the original bulk gap was shifted upward and the Fermi level was shifted downward no ...
10
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1answer
224 views

How to make sure that my SCF calculation is correct?

hope you are doing well. I am trying to study the electronic properties of ZnO doped with transition metals (Co, Ni, Fe) using DFT calculation, I am a beginner on DFT calculation using quantum ...
12
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1answer
108 views

Structure relaxation of a thin film structure in VASP

I have some general questions about doing the structure relaxation of a thin film structure in VASP. I want to study the how the band structure evolves as we increase the number of layers of the ...
11
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1answer
77 views

Is there any relation between static correlation and finite-temperature smearing?

I am new to this field, so there is a chance that I am mixing two entirely different concepts together, but it seems to be that static correlation and finite-temperature smearing in DFT are somehow ...
5
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38 views

How to use hp.x in Quantum ESPRESSO to calculate Hubbard parameter

I want to work with GGA +U on Quantum espresso to calculate the electronic properties of Ni Co co-doped ZnO system, but I can't figure out how to use the hp.x program for my system to calculate the ...
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57 views

Band structure has unusual lines in the valence band using Quantum ESPRESSO

Currently, I am working on ZnO doped with nickel and cobalt. I performed the SCF, NCF, BANDS calculation and got the results, the calculation converges without any errors. After that I used BANDS.X to ...
12
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1answer
88 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 ...
9
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1answer
100 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. ...
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34 views

What correlation effect are included in KS-DFT with LDA and GGA?

This post is inspired by this post: What correlation effects are included in DFT? The Kohn-Sham density functional theory (KS-DFT) are considered to be exact and can include all correlation effects in ...
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Is there a way I could calculate the pressure and use SOC at the same time?

I have been trying to find the appropriate k-point grid via convergence in quantum ESPRESSO (QE). The following is my input file. ...
7
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2answers
175 views

What is the meaning of the “PRIMCELL.vasp” file generated by VASPKIT tool during bandstructure inputs generation?

When I use VASPKIT tool to generate K-path KPOINTS file for Bandstructure calcualtion of a 4x4x1 supercell of a pure material, ...
11
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2answers
667 views

What's the relationship between the first HK theorem and the second HK theorem?

The first Hohenberg-Kohn (HK) theorem: The external potential $v(\vec{r})$ is determined, within a trivial additive constant, by the ground-state electron density $\rho(\vec{r})$. From basic quantum ...

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