# Tag Info

## Hot answers tagged vasp

7

The band extrema may be at an arbitrary point in the Brillouin zone, so determining their position can become computationally demanding. The following strategy is something that is sometimes used to locate Weyl points (band crossings) in a band structure, which I think should also be useful for locating band extrema. The strategy would be: Sample the full ...

6

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 level is set to VBM.

6

You can start with this bash script for Aluminum to begin Note: Make sure to fix two quantities while changing third one among INCAR,KPOINTS,POSCAR Lattice optimization for i in seq -w 4.01 0.01 4.05 # change the range needed do cat <<EOF >POSCAR Al bulk FCC $i 0 0.5 0.5 0.5 0 0.5 0.5 0.5 0 1 direct 0.0 0.0 0.0 EOF mkdir$i cp INCAR $i/ cp ... 5 I think you will be hard pressed to find a definitive answer, however I would say you are within reason to call it a half semiconductor. Just be aware that this doesn't seem to be a well defined term and you may need to give the audience / reader a prompting on what you mean by half semiconductor. 5 In addition to ProfM's answer, for many materials it's typical for the band extrema to be on high symmetry points or lines. Sampling these lines can often help you find the extrema or a point close to it. However, there are several schemes for determining what lines in$\mathbf{k}\$-space to sample, including: The scheme from Setyawan and Curtarolo https://...

4

For the up-spin channel, you can absolutely consider it as a semiconductor; for the down-spin channel, you can consider it as an insulator (may someone also consider it as a semiconductor, just different conventions). Thus, you can say your material is a half-semiconductor (HSC). (HSC is a semiconductor in one spin channel but an insulator in the other spin ...

4

Ionization energy is more appropriate for isolated atoms, you want the workfunction or ionization potential of your alloy surface. You calculate this usually from slab calculations because there is explicit vacuum. Work function is defined as: $$\Phi=E(vacuum)-E(Fermi)$$ If you use vasp this can be useful https://github.com/WMD-group/workfunction And a very ...

2

Firstly due to the bandgap problem in density functional theory, the bandgap is underestimated (difference between valence band maximum and conduction band minimum). However, for semi-conductors, hybrid functionals such as HSE06 do a good job of predicting the bandgap. However, such calculations would be computationally expensive. To find the conduction band ...

2

Your interpretation of the results. I agree with you that if you find no imaginary frequencies in the cubic phase it means it is at a local minimum of the potential energy landscape, and that if you do find imaginary frequencies for the tetragonal phase, then that one is at a saddle point. I also agree that a phase exhibiting imaginary frequencies may be ...

2

As the error indicate: | Your generating k-point grid is not commensurate to the symmetry | | of the lattice. This can cause slow convergence with respect | | to k-points for HF type calculations | | suggested SOLUTIONS: | | ) if not already the case, use automatic k-point generation | | ) shift your grid to Gamma (G) (e.g. required for hex or fcc lattice) | ...

1

There is a discussion on this limitation on VASP page. Maybe the approach of a frozen f valence PAW pseudopotential could help you. Although magnetic properties might not be as well represented. I'm quantum espresso user and when their PAW potentials show problems (not so rare) I go to a norm-conserving solution like pseudodojo library, if you can do this in ...

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