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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 ...
Phil Hasnip's user avatar
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11 votes
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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 ...
elutionary's user avatar
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9 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 ...
Jack's user avatar
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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 ...
Jack's user avatar
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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, ...
freude's user avatar
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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 ...
Tristan Maxson's user avatar
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 ...
Peter Schindler's user avatar
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 (...
Phil Hasnip's user avatar
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7 votes
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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 ...
Phil Hasnip's user avatar
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6 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 ...
Leon A's user avatar
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6 votes
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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 \...
Camps's user avatar
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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 ...
Phil Hasnip's user avatar
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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 ...
Camps's user avatar
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3 votes

Which software to model Fermi level position of graphene in an external electric field?

SIESTA With SIESTA and its TranSIESTA module, you can model all you are looking for. From the SIESTA site: SIESTA is both a method and its computer program implementation, to perform efficient ...
Camps's user avatar
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3 votes
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Question about determining Fermi energy in Quantum espresso

I have repeated your SCF calculation with SSSP precision pseudopotentials without doing any convergence testing and using the suggested minimum values. The input and the output files are attached at ...
Abdul Muhaymin -Free Palestine's user avatar
3 votes
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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 ...
Youssef Chlikhy's user avatar
3 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 ...
Youssef Chlikhy's user avatar
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 ...
Memories's user avatar
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