Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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4
votes
0answers
46 views

What are the challenges in using DFT to study the Hydrogen Evolution Reaction of (111), (110), (100) and (011) planes of Cobalt (III) Phosphide (CoP)

What are the challenges in using DFT (implemented in the VASP code) to study the hydrogen evolution reaction (HER) of the (111), (110), (100) and (011) surface planes of Cobalt (III) Phosphide CoP.
6
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1answer
126 views

Why does it take 5-10 steps to obtain reasonable orbitals during initialization in VASP?

I am trying to figure out the initialization process of VASP, and I found an INCAR tag NELMDL, on the wiki page of NELMDL, it is said that VASP requires 5-10 steps to obtain the reasonable orbitals. ...
11
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2answers
446 views

Why the band structure of a slab is not smooth?

I am trying to calculate the band structure of a TiO2-Rutile slab, but the result I got is not very smooth, and the result shows it is an indirect gap material, but the bulk phase of TiO2-Rutile is a ...
8
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1answer
97 views

Citing a pseudopotential

I conduct my DFT calculations using the SIESTA DFT package. For this, I obtained the pseudopotentials from this site which says that they have obtained the data from the Abinit database. However I do ...
6
votes
1answer
34 views

How to determine the right k-points for the band structure of a slab?

I am trying to compare the band structure of a slab and the bulk phase, just like the example on the VASP wiki. In the example of VASP, it calculates the band structure of the slab of Ni metal. A slab ...
6
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2answers
48 views

DOSCAR file during structure relaxation is useless?

I am trying to figure out why the DOSCAR file during structure relation is useless, for the last step of structure, the atoms' positions are almost fixed, is that the same as a static calculation? But ...
12
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1answer
140 views

Why are condensed matter predictions considered on par with experiment, while structural biology modeling receives more skepticism?

I have two main modeling research lines: one related to structural biology (including rational drug design, de novo design, polymorphism, etc.) and the other one related to condensed matter (...
7
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1answer
45 views

SIESTA error: must be in PAO.Basis, (it has semicore states)

I keep getting this error with Siesta every time I do a calculation, ...
7
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0answers
50 views

Simulate plasma-material interactions (PMI) using Density Functional Theory (DFT)? [closed]

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

Different between ENCUT and ENAUG in the VASP setting?

I am trying to figure out the difference between ENCUT and ENAUG in VASP settings, I found the following description on the wiki of VASP. ENAUG specifies the cut-off energy of the plane wave ...
6
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1answer
49 views

Is it necessary to do self-consistent calculation after structure optimization?

When calculating the band structure of a material, I have been told that at first, I need to do structure optimization to get a stationary structure(1st step), and then keep the atoms' position fixed, ...
3
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1answer
71 views

Job stops in between without showing any error

I am trying to calculate the dos of one bulk system. My dos calculation job stops in between without showing any error. Here I am attaching the link of my input dos calculation files. CONTCAR file is ...
9
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0answers
66 views

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

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 ...
7
votes
1answer
94 views

Why am I getting DOS like this in Quantum ESPRESSO?

I am working on $\ce{GeHfTe}$ and in the case of a non-collinear calculation, I am getting the DOS in the attached photo. I have already relaxed my structure with VC-relax and it is converged with ...
13
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1answer
126 views

Physical interpretation of k-points

What is the Physical interpretation of the k-points used in ab initio calculations? Why must the number of k-points be optimized rather than just using some large fixed number of them?
5
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1answer
56 views

Smearing values for different codes

I am using Quantum Espresso along with a different code, I am performing calculations on Platinum bulk. After choosing the "cold" smearing (which I read is a good choice for metals) with a ...
5
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1answer
45 views

Case study: KPOINT and band parallelization in Quantum ESPRESSO

I am testing Quantum ESPRESSO with different values for Npool and bands in order to calculate run time. ...
8
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1answer
37 views

Does the INIWAV tag in VASP assume that the wavefunctions are plane waves?

I am trying to figure out how to set the initial wavefunction in VASP, on the VASP wiki page of INIWAV, it is said that VASP would fill wavefunction arrays with random numbers. ...
7
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1answer
35 views

Are CHARGE=2 and INIWAV=1 contradictory in the VASP setting?

When initializing the charge density in VASP, I set the parameters as follows: ...
6
votes
1answer
100 views

Lattice Thermal conductivity calculation error

I have been trying to calculate Lattice Thermal Conductivity on my system using QuantumEspresso. I used phonopy and phono3py. I was successful to run these codes on Si system for practice. Now when I ...
4
votes
1answer
53 views

How to understand the energy derivative of the logarithmic derivative of a wavefunction when deriving norm-conserving pseudopotentials

The 4th desirable property of a norm-conserving pseudopotential given by Hamann et al is for the 'logarithmic derivatives of the real and pseudo wave function and their first energy derivatives agree ...
6
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0answers
70 views

How to identify/treat delocalized pi bonds in DFT

For a structure such benzene, the pi bonds between the carbon atoms are said to be de-localized. Therefore the electrons are expected to be exchanged in between individual C-C bonds. When dealing with ...
9
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0answers
119 views

How to interpret WannierTools Python code that generates tight-binding model in the wannier90_hr.dat format? [closed]

I am getting myself acquainted with Wannier Tools. Wannier Tools requires two inputs, a wt.in file, and a .dat file. This ...
6
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1answer
132 views

How does electronic iteration work in a VASP relaxation calculation?

I am a beginner using VASP to do material modeling, and I'm confused about the following questions: How does the electronic iteration work in VASP relaxation calculation? Is the electronic iteration ...
6
votes
2answers
88 views

Relation between lattice parameter and energy for relaxations

We have been wanting to do relaxation of lattice parameters as a function of the energy. I want to know the mathematical expression for this, and also the theoretical background related to this method....
8
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1answer
267 views

Study of supercell after creating vacuum

For studying a bulk supercell, after creating some vacuum in it, I'm confused about how to relax it. With VASP, I can do relaxation using NSW = 0 and ...
8
votes
1answer
82 views

what do I need to change about typical VASP input file to calculate the energy of a single atom?

I'm a little confused how to make a VASP input file to calculate the energy for the isolated atom: Do I need to change the lattice parameter of my unit cell or can keep the value for the whole system?...
6
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0answers
28 views

TIP5P model for water in RISM [closed]

I want to use the implementation of ESM-RISM from the Otani laboratory using Quantum Espresso. For my system I ask for $H_2O \; (H^+Cl^- \; 1M \; aq.)$, following the literature the best way to ...
9
votes
1answer
67 views

How to confirm whether a system is mott-insulator or not from DFT calculations?

I am using Quantum-Espresso and I need to study mott-insulator. Being a beginner, I am not sure, how do I confirm whether my system is a mott-insulator or not?
9
votes
1answer
65 views

How to identify localized surface states in the band structure

After calculating the band diagram of a structure, is there a way to identify localized surface states? I am working with Si nanowires with different cross sections. I want to determine the band gap ...
6
votes
2answers
76 views

SIESTA output wavefunctions: all vs selected?

Using SIESTA, I want to plot the wavefunctions around the Fermi level (similar to HOMO/LUMO). Also, I want to do COOP analysis. From the SIESTA manual, I can setup to write the wavefunctions ...
12
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0answers
111 views

Orbital-free DFT and Density Functional Tight-Binding: Comparison [closed]

There are many flavors of DFT that are alternative to, or go beyond the Kohn-Sham formulation (KS-DFT). Some of these are based on approximations that sacrifice accuracy when compared to KS-DFT, but ...
5
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1answer
44 views

How to fix local magnetic moment of each ions in VASP?

In spin-polarized calculation,total magnetic moment can be fixed to a specific value using NUPDOWN tag. In non-colinear spin calculation, tag ...
8
votes
1answer
115 views

How to evaluate the electron relaxation time of nanostructures computationally

I am working with Si nanowires using the SIESTA ab initio code and the BoltzTraP2 Boltzmann transport equation solver. However, the output of the BoltzTraP2 code comes per relaxation time (...
6
votes
1answer
65 views

How can I build an MoS2 nanoribbon?

Are there any codes available? What is the easiest way?
8
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0answers
87 views

Calculate FF interaction energy of small molecular dimers

I have a set of molecular dimers (~25 atoms) for which DFT-D3 interaction energies are calculated by Psi4 and Turbomole program. Now I want to compare these values against Force-Field methods like UFF/...
7
votes
0answers
102 views

Equations related to the first-order derivative of the wavefunction [closed]

I have two brakets (the angular momentum matrix elements) that are $$ \langle \partial_\mathbf{k} \psi_{n \mathbf{k}} | \times \mathbf{p} | \psi_{m \mathbf{k}} \rangle \tag{1} $$ $$ \langle \psi_{n \...
9
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1answer
129 views

Geometry optimization using DFT

I have been attempting to optimize the structure of a Si nanowire using SIESTA. The original structure fed into the optimization is as follows. Once it is optimized, the structure would change to ...
11
votes
1answer
162 views

Using "soft" constraints / bias in geometry optimization?

I study molecules weakly bound to nanoclusters and surfaces. During geometry optimization, I often run into problems like for example a small metal cluster behave nicely and has a given, stable ...
9
votes
1answer
452 views

Kramer's Degeneracy and Antiferromagnetism

How can one understand the concept of Kramer's Degeneracy for an antiferromagnetic system where spin-up and spin-down bands overlap due to net zero magnetic moment?
6
votes
1answer
51 views

How do I relax only the in-plane component of the unit cell?

I know that &CONTROL='vc-relax' option calculation performs a unit cell relaxation, and that the ATOMIC_POSITIONS can be ...
15
votes
5answers
462 views

What are some open-source all-electron DFT alternatives to Wien2K?

Since the beginning of the century, Wien2K has proven to be a very powerful player in computational condensed matter and materials physics. Wien2K is an all-electron periodic DFT code based on the ...
7
votes
1answer
87 views

Different band gap observed in unitcell and in the supercell

I calculated the bandgap for one system in the unit cell and in the supercell of 2x2x1 and 3x1x1. Although 3x1x1 gives the same bandgap as I got from the unit cell (1.79 eV) but 2x2x1 is giving 1.75 ...
9
votes
1answer
180 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 ...
6
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0answers
49 views

Comments on the electronic relaxation time variation between nanowire configurations

I am studying Si nanowires with different cross sections. In my work, I plan to evaluate the thermoelectric performance variation between different configurations. To achieve this, my current approach ...
8
votes
2answers
109 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-...
10
votes
0answers
81 views

Single electron transfer periodic DFT in VASP

I have the following question: I am currently studying the electrocatalytic $\ce{CO2}$ reduction reaction (CO2RR) on $\ce{Cu}$ materials using periodic DFT calculations and I am using the ...
9
votes
0answers
50 views

Is it possible to construct a tight binding matrix of high atomic layer thin film from the lower one?

Given a tight binding matrix of a thin film system with a few atomic layers, is it possible to construct a tight binding matrix of higher atomic layers thin film from the lower one? For example, I ...
7
votes
0answers
139 views

The gap was open when I was doing an HSE + SOC DFT calculation [closed]

I used VASP as my DFT software to do a calculation on an anti-perovskite crystal. I try to reproduce the band structure from literature which was calculated based on HSE + SOC calculation. Their ...
6
votes
0answers
191 views

Is there any way to simulate the Polarization vs Electric Field loop of BaTiO3 using Quantum ESPRESSO? [closed]

I'm new to the Quantum ESPRESSO package. There are articles outlining the procedure of indirectly simulating the P-E loop of piezo-electric materials via Berry phase calculations.One procedure is ...

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