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Questions tagged [bandgap]

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7 votes
1 answer
266 views

Materials with low band gap and low conductivity simultaneously. Is it possible?

I'm working on a data-driven project involving material properties and I'm wondering about the following: I know that the notion of band gap and electrical conductivity are inversely related, and the ...
James Arten's user avatar
7 votes
1 answer
408 views

How to find the band gap energy value in Quantum ESPRESSO?

Does anyone know in which of the DOS output files I can find the band gap energy value of my material? I'm using Quantum ESPRESSO.
Caroline Santos 's user avatar
4 votes
1 answer
389 views

How to choose the best U value for studying the electronic properties?

I'm new to DFT+U and trying to understand how FeTiO3 works by looking at its electronic properties. But there's a big problem: when I use normal DFT, I can't get the w right band-gap value. How can I ...
Prasad's user avatar
  • 101
0 votes
0 answers
30 views

Spaces in Electronic band structure

I keep getting this whenever I try plotting the electronic band structure for CoRhMnGa on quantum Espresso, what could possibly cause the vertical spaces
Jeremiah Okotie's user avatar
5 votes
1 answer
124 views

Can a material be a conductor in one direction and a semiconductor in another direction?

I know that semiconductors have a band gap, and conductors have bands that cross the Fermi level. However, can a material have a band gap for certain $\vec k$ regions but bands cross the Fermi level ...
Vladislav Gladkikh's user avatar
4 votes
1 answer
157 views

Band gap do not match to published result in DFT using BURAI GUI of Quantum Espresso

I am just learning DFT using the BURAI GUI of Quantum Espresso.I took the CIF file of a structure from the Materials project database. It is well vc-relaxed and conversed easily but gives the band gap ...
mm Gururani's user avatar
1 vote
0 answers
78 views

Is it possible to generate an input file for band structure calculations for multiple KPaths at once? [closed]

I need to generate an input file for band structure calculation along the following k path. how do I input the k path in the "bands.in" file? here, i need to calculate the band gap along all ...
Prasad's user avatar
  • 101
6 votes
1 answer
117 views

Determining the Nature of a Material's Band Structure: Metallic or Semi-Metallic?

I have obtained a band structure plot (see image below) for a crystalline material. The Fermi level is set at the zero energy level. Based on the band structure, I am uncertain whether the material ...
Jaafar Mehrez's user avatar
3 votes
0 answers
63 views

My INCAR file, POSCAR, and KPOINTS are same for GGA, however after the PBE calculation, I found that the bandgap is Changing. Why is that happened?

INCAR, POSCAR, and KPOINTS are the same but for the same calculation, the bandgap is changing. First, I relaxed the structure then did the self-consistent calculation, and bandstructure calculation. ...
Ashfaq Ohi's user avatar
5 votes
3 answers
232 views

How do I obtain CB and VB values from Quantum ESPRESSO?

Can someone explain to me please how am I supposed to get this: From this: I'm a little bit confused because in my calculations using Quantum ESPRESSO I found that: ...
Camilla's user avatar
  • 2,169
2 votes
0 answers
50 views

How to know if the band calculation result is correct? [closed]

I did a band calculation (I'll leave the input and output files below), but I don't know how to identify whether my result is right or wrong, can anyone help me? Arquivo.in ...
Caroline Santos 's user avatar
1 vote
0 answers
54 views

Indirect to direct bandgap transition in SUPERCELLS and band unfolding

In a related question: Indirect to direct band gap transition in SUPERCELLS it is illustrated that one just can't immediately tell from a supercell's bandstructure plot whether the bandgap is direct ...
Sha's user avatar
  • 500
5 votes
1 answer
104 views

Indirect to direct band gap transition in SUPERCELLS?

My compound under investigation are cubic and construct corresponding 2x2x2 supercell. Properties like optical and mechanical seem to be correct as expected. However a problem arises in their ...
Bernard's user avatar
  • 51
4 votes
0 answers
322 views

Interpretation of total energy in SCF calculation using Quantum Espresso [closed]

I am performing SCF calculations using Quantum Espresso for crystalline materials to determine the band gaps and energies. A sample output for one of the crystals is shown below. ...
Prashant Govindarajan's user avatar
6 votes
1 answer
281 views

Negative band gap in DFT calculations

I am performing DFT simulation (with Quantum Espresso) for a large number of crystalline materials to estimate their band gap energies. I am getting negative band gap values for many of them (...
Prashant Govindarajan's user avatar
7 votes
1 answer
298 views

Which strategy of improving the DFT band gap is the most effective?

DFT band gap problem is a well-known problem. LDA or GGA exchange-correlation functionals underestimate the band gap heavily. I saw some of the strategies to address this issue were: using hybrid ...
Abdul Muhaymin -Free Palestine's user avatar
6 votes
0 answers
49 views

Benchmarking DFT vs Experimental Gaps - Confusion over Fundamental and Optical Gaps

Recently, I've come across discussions about the differences between fundamental (or electronic) bandgaps and optical bandgaps, with the two quantities differing mainly by the electron-hole binding ...
CW Tan's user avatar
  • 1,316
2 votes
0 answers
36 views

Doping induced overall bandgap narrowing vs. bandgap narrowing achieved by localized doping induced level

Doping is an efficient strategy to narrow the bandgap of wide-bandgap metal oxides, in order to harvest more light. Let's consider the mechanism by which doping reduces the bandgap of a metal oxide ...
meTchaikovsky's user avatar
2 votes
1 answer
405 views

Problem with k-points with pw2wannier

I am calculating the band structure using HSE06 using wannier method. I have manage to perform the scf calculations and first processing of wannier.x to generate the .nnk file. but when I run the ...
Mubarak Yagoub's user avatar
2 votes
0 answers
50 views

What's the meaning of a Hubbard term determined by repeated investigation? [closed]

In the paper bellow they used GGA+U to investigate the structural, electronic and optical properties of Ag- and Cu-doped ZnO. https://www.emerald.com/insight/content/doi/10.1108/MI-05-2022-0088/full/...
Camilla's user avatar
  • 2,169
2 votes
0 answers
113 views

How to determine high-symmetry points in case of PBE0 using Quantum ESPRESSO? [closed]

Normally when we use PBE-GGA as an approximation we can determine the high symmetry points in x coordinate from the output file of bands.x calculation . But in the ...
Camilla's user avatar
  • 2,169
5 votes
1 answer
941 views

Extracting band structure data using Boltztrap for Quantum ESPRESSO

I used PBE0 in my calculations using Quantum ESPRESSO . I have ran a scf calculation then I used Boltztrap by running the command btp2 -vv interpolate -m 3 ./ then <...
Camilla's user avatar
  • 2,169
6 votes
2 answers
390 views

Optical Band gap determination from absorption coeffecient using DFT

I am currently working with a perovskite material which shows forbidden transitions. Older studies used bigger values of $\alpha$ in HSE06 calcualtions(to match with experimental Band Gap) but a ...
Chan's user avatar
  • 649
4 votes
0 answers
74 views

Do the orbital energies of ground-state Dyson orbitals exactly capture arbitrary excitation energies and/or ionisation potentials/electron affinities? [closed]

According to an answer to my question on whether the Kohn-Sham orbital energies theoretically exactly capture arbitrary ionisation potentials and/or excitation energies, the answer is no for both ...
Kanghun Kim's user avatar
5 votes
1 answer
155 views

Question on generalised Kohn-Sham "band gap"

It is often said that the optical band gap, i.e. the first excitation energy, of a species is exactly equal to the difference between the (Kohn-Sham) HOMO and LUMO. This would mean that the state of ...
Kanghun Kim's user avatar
5 votes
1 answer
513 views

Direct and Indirect bandgap

How can I know which one is direct bandgap material and which one is indirect? Why does Germanium have an indirect bandgap? How can be it become a direct bandgap material? Here, I have attached a ...
Farjana Mahajabin's user avatar
4 votes
0 answers
198 views

The comparison of bandgap value of slab and bulk phase [closed]

I tried to calculate the bandgap of the TiO2-Rutile bulk phase, DFT(not +U) calculation shows the bandgap is about 1.8eV, which is roughly the same as the 1.78eV on the Material Project. When ...
Jack's user avatar
  • 2,057
2 votes
0 answers
128 views

How would surface state affect the band gap value of semiconductors? [closed]

I am struggling to figure out the relationship between bandgap value and surface states. To my understanding, when considering the material that includes surface, there would be some surface states in ...
Jack's user avatar
  • 2,057
5 votes
0 answers
673 views

How to get the right type of bandgap(indirect/direct) in VASP? [closed]

I am trying to calculate the band gap type(Direct or Indirect) of TiO2-Rutile, according to the Material Project, rutile is a direct bandgap type semiconductor. The VBM and CBM are both at the Gamma ...
Jack's user avatar
  • 2,057
7 votes
1 answer
526 views

What parameters should be checked on both unit cell and super cell to make sure the calculations are going fine?

Question is based on further learning about the previously asked question - Do NSCF calculations on Supercell gives different band gap than the Unit Cell? How should I compare SCF and NSCF ...
epsilon02fft's user avatar
  • 1,522