12
votes
Determining Fermi energy in density functional theory
The Fermi energy is defined implicitly, by requiring that the total of the band occupancies $f$ is the number of electrons, $N$:
$$\sum_{b=0}^{N_b}f_b=N\tag{1}\label{occ}$$
where $N_b$ is the number ...
- 6,582
11
votes
Accepted
Fermi Energy in Band Structure
In electronic structure calculations of finite systems, there is a well-defined energy scale: 0 is the vacuum energy, and any electron with positive energy is unbound.
For materials, the story is ...
- 766
8
votes
Determining Fermi energy in density functional theory
Usually, it is assumed that the Fermi energy is the energy of the highest occupied electronic state. It is well defined for metals with partially filled bands. For semiconductors and dielectrics, ...
- 340
8
votes
Accepted
If Gaussian and Tetrahedron smearing method lead to different Fermi energies, which one is the correct?
ISMEAR=-5 gives you the correct Fermi energy.
Usually, the Fermi level is set to the VBM.
If you shift the BS by the Fermi energy from the DOS calculation with ISMEAR=-5, you will find your Fermi ...
- 14.9k
8
votes
How can I simulate the work function given by Ultraviolet Photoelectron Spectrum (UPS)?
You can use Galore package.
Galore is a package which applies Gaussian and Lorentzian broadening to data from ab initio calculations, such as VASP.
The two main intended applications are:
Gaussian ...
- 14.9k
8
votes
Find the value of density of states at the Fermi energy using VASP
Let me suggest a simple answer, although I am not convinced you will get anything sufficently different for the fermi level than just using a converged grid.
Consider a range of energies such as 10 ...
- 10.8k
7
votes
Determining Fermi energy in density functional theory
This has been answered very well already but just to add a practical note: For semiconductors, Vasp places the Fermi level at the valence band maximum ($\pm$ smearing energy) whereas Quantum Espresso ...
- 466
7
votes
Mobility and chemical potential
In this case, $\mu$ refers to the chemical potential. The reason it is given as $\mu-E_f$ is simply to highlight that the "zero" has been set to the Fermi-level of the reference calculation (...
- 6,582
7
votes
Accepted
Fermi energy lower than valence band maximum?
No, this isn't possible for an undoped semiconductor. The reason it's happening is because the Fermi level is not well defined for your semiconductor at finite temperature, and you're trying to read ...
- 6,582
6
votes
Accepted
Mobility and chemical potential
If you go to the definition of the Seebeck coefficient ($S$) you will find:
$$S = \frac{{e{k_B}}}{\sigma }\int {d\varepsilon \left( { - \frac{{\partial {f_0}}}{{\partial \varepsilon }}} \right)} \Xi \...
- 22.3k
5
votes
SC vs NSC Fermi energy in VASP, which is correct?
When you do the ground state calculation, you choose a k-point mesh to numerically integrate the states over the Brillouin zone. This is an approximation, but a controllable one; if you increase the ...
- 6,582
5
votes
How do I obtain CB and VB values from Quantum ESPRESSO?
From the graph you presented:
Select the Brillouin $\Gamma$ point, $G$ in the graph (this is for a direct gap system).
Look for where the Fermi level is. In the graph, it is indicated by the red ...
- 22.3k
4
votes
How do I obtain CB and VB values from Quantum ESPRESSO?
I would recommend to obtain VB top and CB bottom energy values from the output file. The occupation numbers are listed if 'verbose' mode is active. In any output mode the energies should be printed ...
- 61
3
votes
Accepted
How to find the Fermi energy with highest occupied and lowest unoccupied level from a single nscf caculation using quantum espresso?
I don't think it is possible as it is required to use a smearing method in order to obtain the fermi energy. By doing so, you can not get the values of HOMO and LUMO levels. so obtaining both of them ...
- 166
2
votes
How do I obtain CB and VB values from Quantum ESPRESSO?
To obtain both the VB and CB you will have to run scf calculation by using the nbnd command (the number of Kohn-Sham states) with a value basically the same as the ...
- 166
2
votes
Is it easier to obtain n-type TiO2 in reducing environment than in oxidizing environment?
The synthesis environment can be modeled by the chemical potential of chemical component elements, not by the chemical potential (or Fermi level) of eletrons. When O is rich, the material would ...
- 353
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