What parameters should be checked on both unit cell and super cell to make...
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 calculations...
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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...
View ArticleHow 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...
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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...
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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 picture...
View ArticleQuestion 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...
View ArticleDo the orbital energies of ground-state Dyson orbitals exactly capture...
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...
View ArticleOptical 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 recent...
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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 btp2 -vv integrate interpolation.bt2...
View ArticleHow to determine high-symmetry points in case of PBE0 using Quantum ESPRESSO?...
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 case of PBEO we can't run a bands.x...
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What's the meaning of a Hubbard term determined by repeated investigation?...
In the paper bellow they used GGA+U to investigate the structural, electronic andoptical properties of Ag- and Cu-doped...
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Doping induced overall bandgap narrowing vs. bandgap narrowing achieved by...
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...
View ArticleBenchmarking DFT vs Experimental Gaps - Confusion over Fundamental and...
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...
View ArticleWhich 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...
View ArticleNegative 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...
View ArticleInterpretation of total energy in SCF calculation using Quantum Espresso...
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. highest occupied,...
View ArticleIndirect 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...
View ArticleIndirect 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 or...
View ArticleHow 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&bands outdir='./tmp'...
View ArticleMy INCAR file, POSCAR, and KPOINTS are same for GGA, however after the PBE...
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....
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