Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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4
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1answer
85 views

One-to-one correspondence between electron density and external (Coulomb) potential

I calculated the electron density of a molecule by a DFT software (Gaussian 16) with a standard setting in terms of the basis set and hybrid functional. After that calculation, I viewed the plot about ...
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0answers
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How can I calculate the exchange energy for a molecule in PySCF?

I am trying to generate exchange energy separately in pyscf but didn't see a way to do that. For correlation energy, it's fairly simple but do you have any idea how to calculate exchange energy?
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Crystallography: How to sample *unique* structures from configuration space? (binary alloy supercell)

I'm working with a binary alloy system (call it 'AB'), and I'd like to generate a few unique configurations for DFT purposes. My primitive cubic unit cell consists of 4 atoms; i.e. 4 positions. Thus, ...
4
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1answer
53 views

List of software for creating random multi-component alloy inputs for DFT or MD

I'm looking for a list of tools similar to ATAT which are available for creating random multi-component alloy inputs for DFT/MD.
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2answers
269 views

DFT functionals from MP2 methods

I have heard people talk about DFT functionals built starting from MP2 corrections. Do you happen to have a reference I read about that from?
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39 views

Bloch wave function extraction for the specific k-points and specific band from QE calculation

I would like to use QE to obtain u_K(r), which is the Bloch wave function of spin-up maximum valance band at K point. If I define the K point in the input file and do a scf calculation by QE including ...
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46 views

Calculating lattice thermal conductivity using Quantum ESPRESSO and phonopy

How should I calculate lattice thermal conductivity in Quantum ESPRESSO? I have installed phonopy. My Linux distribution is Ubuntu.
11
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1answer
291 views

Does the spin polarised DFT calculation mean broken time reversal symmetry?

Recently, I have got to learn that if time-reversal symmetry and inversion symmetry are present simultaneously in the system we have the following conditions on energy of Bloch's states: $$E_{n,\chi }(...
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HSE06+SOC method using VASP

I have a query on HSE06 + SOC method in VASP. This is a follow-up question to the comment given for a similar question at "https://mattermodeling.stackexchange.com/questions/4269/how-to-carry-out-...
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1answer
117 views

Quantum espresso vs SIESTA

I want to know which particular calculations are suitable for each of them. Is SIESTA free, as in can you work on it without license. (question is based on the fact for now that all these will be done ...
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5answers
2k views

Is Ubuntu the best option for DFT calculations?

I have just started studying DFT. I did some basic calculations using a Windows system. How will Ubuntu help me if I install it on my system? How much space should I allocate on drive for the Ubuntu ...
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1answer
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Why does the PBE XC functional not appear to be a sum of exchange and correlation energy?

In the famous 1996 paper of Burke, Perdew and Ernzerhof in the very first paragraph it is stated that $E_{XC} = E_X + E_C$. Then, a GGA functional is derived starting from the energy density of ...
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Quantum confinement of transition metal dichalcogenides (TMDs)

TMDs (transition metal dichalcogenides) are materials that can have a layered structure. When moving from bulk to monolayers, the bandgap changes from indirect to direct according to the image (DFT to ...
7
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1answer
427 views

Why is my ORCA calculation of nitrogen iodide failing?

I am using ORCA version 4.2.1 to calculate on the RI-BP86/def2-SVP level of theory the molecule $\ce{NI3}$. I would assume this to be a rather trivial matter, but I am running into an error. I've only ...
7
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1answer
67 views

Visualize electron density using pyscf

I found the following example of code which uses density functional theory to compute the electron density $\rho$: ...
10
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1answer
158 views

External potential in the Hohenberg-Kohn map

I have read the following paper, "Bypassing the Kohn-Sham equations with machine learning", published from Nature Communications in 2017. https://www.nature.com/articles/s41467-017-00839-3 ...
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Is it possible to simulate plasma-material interactions (PMI) using Quantum ESPRESSO? [closed]

I am separately learning about materials modelling using Quantum ESPRESSO (QE), and the theory of plasma-material interactions (PMI). This made me wonder: Is there any way to model PMI using QE even ...
5
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1answer
46 views

Can a CHGCAR file be converted into a CIF file?

A .cif file can be used for multiple purposes and is a more generic format to store atomic data.
4
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1answer
79 views

How to process electron-density data from a CHGCAR for better handling?

We all know that Vesta helps us visualize the electron clouds present in the CHGCAR data, but I am looking for a better way to process the electron-density data we get in a CHGCAR file for compact ...
6
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2answers
163 views

POSCAR data file for a 2D system

I would like to understand how to calculate the band structure of the Graphene monolayer system using DFT. I am using VASP for material simulation. My question is how to write the crystal structure ...
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36 views

The quantum spin Hall phase with Z2 = 0?

I used first principle calculations to study the thin film model. An obvious crossing was shown to appear at the gamma point when the edge state was calculated, which was originally predicted to be ...
7
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2answers
121 views

What is the format of the electron-density data in a CHGCAR file?

Rephrasing the above, what is the pattern in which the electron-density data is stored in the CHGCAR file? I understand that the electron density data in a CHGCAR file is in the form of a 3D Fortran ...
6
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1answer
155 views

Keesom and Debye forces in DFT

Do van der Waals corrected DFT functionals include Keesom and Deby corrections too or just London dispersion? Because when I look at these methods in detail, I see that there is just an attempt to ...
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35 views

Calculating emission spectrum of organic compounds by DFT. Can someone elaborate in terms of calculating it for aggregatrion induced emission? [closed]

I am planning for the calculation of emission spectra of organic compounds showing the phenomenon of aggregation-induced emission (AIE). Can someone help me get started?
8
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1answer
67 views

Benchmark test cases for DFT program or VASP?

Cross-posted on reddit/comp-chem. I am trying to build my workflow of using DFT to predict properties of some materials, but I am not sure if I do it all right, so I think there might be some ...
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1answer
75 views

Why does the S squared value have no meaning in Density Functional Theory?

It is not the first time that I stumble upon the affirmation that spin and the $S^2$ value, under DFT, has no "real physical meaning". Why? If that is true, why are we using it all the time ...
12
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1answer
127 views

Creating Interatomic Potential for Lammps using DFT

What are the basic steps and methodologies used in creating inter-atomic potential (specially EAM, MEAM potentials) for metals ...
8
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1answer
250 views

Energy cut-off test meaning in atomic-like basis functions' DFT

I have been using SIESTA code to perform some practicals in my college and I have run energy cut-off tests before calculating properties of semi-conductors or insulator. As far as I am concerned, ...
4
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1answer
74 views

VASP GW+SOC band structure calculations

How may I carry out GW+SOC a band structure calculation using VASP? Could anyone familiar describe it step-by-step? I could not find any info regarding this on the VASP wiki.
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2answers
84 views

Can the NCI (noncovalent interaction) index be generated starting with psi4?

Can NCI[1] index plots be generated starting from psi4? I'd be happy to just generate the NCI index values and mesh the isosurface myself. With a long-term goal to visualise various medicinal-...
11
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1answer
108 views

Geometrical Optimization not converging, where am I going wrong?

I am trying to obtain the optical properties of ZnSe Quantum Dots, the problem is that my geometrical optimization is not converging. I used VESTA to create the structure(there is a photo in the ...
11
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1answer
619 views

How do we know how much computational power is required for a particular calculation?

So I am super new, although I have gotten the hang of using DFT in Quantum Espresso. I am having a problem with running the calculation for 1.6 nm ZnSe quantum dot. I haven't even gotten to ...
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50 views

How to passivate the surface of ZnSe Quantum Dot and apply vacuum to it? [closed]

I have been trying to simulate ZnSe zinc blende quantum dots using Quantum Espresso and its GUI BURAI. But being a beginner I am a little confused about a few things: How do I passivate the surface, ...
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51 views

Software for calculating the mirror Chern number of 2D systems?

Can anyone please explain to me how can I calculate the mirror Chern number of a 2D system? I will be very thankful if you can refer me to a package or software which can directly perform mirror Chern ...
11
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1answer
231 views

Why is Energy Cut-off and K-Point Convergence necessary in LCAO-based codes like SIESTA?

I am new to DFT-simulation and I wish to understand how it works behind the scene. As the title suggests I don't understand why LCAO-based codes have to define K-points and cut-off energies. I ...
14
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1answer
129 views

Linearized Augmented Plane Wave Method vs. Pseudopotential Methods

While reviewing some DFT literature, I have come across a few papers utilizing the LAPW (Linearized Augmented Plane Wave) method, but I am interested in understanding why exactly one would use these ...
9
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1answer
200 views

Increasing k-point grid to take DOS calculation

I was trying to compute some electronic properties for Pd using SIESTA and VASP for some computer practicals in my university, specially focused on band structure and density of states (DOS) using LDA ...
13
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3answers
549 views

Script to generate input files for benchmark purpose

I would like to run some benchmark of different DFT functionals. The most time consuming part is obviously the generation of the input files. I'm not a programmer, but I think this could be done by ...
8
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1answer
169 views

Why volume of unit cell is not the same as cubing the lattice constant?

I have a cubic-FCC with a=b=c and $\alpha$=$\beta$=$\gamma$=$90^o$. As far as I understand the volume of this cubic unit cell should be a cube of the lattice constant. But this not the case I am ...
7
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1answer
78 views

How to choose a different band path for band structure calculation using VASP?

How can I set a different band path for VASP calculation? For example I want to plot KGMK but not GMKG for graphene?
9
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1answer
145 views

What is the electrical behavior of the material with this band gap?

Presently I am doing DFT calculations to analyse the electronic structure of a material. I got the band structure as shown in the figure. I would like to know the electrical behavior of this material. ...
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81 views

Is “Valence Electron Density” and “Electron Density” data of a molecule the same thing? [closed]

I'm wondering specifically in the context of calculating physical properties from valence-electron-density data using DFT, MD, and or ML (machine learning).
10
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1answer
86 views

Is there a database where one can find the Electron Density data of materials?

The database I am looking for may be experimental, computational or user-generated data. If I end up using the data, I will be providing the necessary citations and credits. Thank You.
10
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1answer
98 views

KS-DFT versus G0W0

The central equation that KS-DFT will solve is: $$\tag{1}\left[ -\dfrac{1}{2}\nabla^2+V_{ext}+V_{hartree}+V_{xc} \right]\psi_i(\vec{r})=E_i\psi_i(\vec{r})$$ Here $V_{xc}$ is approximated with LDA or ...
7
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2answers
55 views

How to take periodic snapshots while running a simulation in VASP?

Same question, rephrased: What is the procedure to take snapshots at fixed intervals while running an AIMD or DFT Simulation in VASP? OR Which parameter in the INCAR file do I modify to achieve ...
8
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1answer
100 views

How to create the structure file for these materials?

I want to create a POSCAR or CIF file file for the monolayers with the data mentioned in the table below : Knowing that the spacegroup is : R-3 (148) Could you please create the POSCAR/CIF for these ...
8
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1answer
79 views

How To calculate formation energy of Ni doped ZnO system in Quantum ESPRESSO?

I have successfully completed the SCF of doped system Ni doped ZnO using GGA+U. I have checked the SCF.out file and found the energy value : E= -6112.0389 Ry. Hwo to calculate the formation energy of ...
7
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1answer
184 views

How to generate Electron Density Fields using DFT?

How may I generate Electron Density Field information using Density Functional Theory calculations? What would my required inputs be like in VASP or Quantum ESPRESSO?
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5answers
688 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
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3answers
546 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 ...

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