Dear Sr.
I am a beginner of VASP. I have very poor knowledge about this software. I made a test calculation by using simple INCAR file. After the calculation, I could not find band gap in OUTCAR file. Could you please tell me where and how I can get the band gap? and if I want to calculate band gap, is there any special setup in INCAR file before the calculation.
Thank you for your help in advance.
This is my INCAR file.
System = Fe8Al4V4
Startparameter for this Run:
NWRITE = 2; LPETIM=F write-flag & timer
ISTART = 0 job : 0-new 1-cont 2-samecut
ISPIN = 2
LWAVE = .FALSE.
LWAVE = .FALSE.
Electronic Relaxation 1
PREC = Medium
NELM = 40;
EDIFF = 1E-04 stopping-criterion for ELM
ENCUT = 300.00 eV
NUPDOWN = 0
DOS related values:
ISMEAR = -5; -4-tet -1-fermi 0-gaus
SIGMA = 0.01
I already succeed in finished the calculation under this condition. However, from both OUTCAR and DOSCAR, I would not find any infromation on how to find the HOMO, LUMO or band gap. I also tried to calculate band structure of this material, I have got the graph for the band structure. However, it is difficult to say exact value for band gap. Could you please give some advices.
Thank you very much in advance.
LvChen from Tohoku univerity
How can I get the infromation of HOMO, LUMO and band gap
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lvchen
How can I get the infromation of HOMO, LUMO and band gap
Last edited by lvchen on Sat Dec 08, 2007 5:18 am, edited 1 time in total.
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How can I get the infromation of HOMO, LUMO and band gap
the band gap is not written in VASP. There are 2 ways to estimate the band gap width:
1) have a look in DOSCAR: the DOS should drop to zero at the Fermi level if your system is insulating/semiconducting, the gap with can then be calculated from the energy differences between the bottom of the conduction band and the top of the valence band.
2) have a look at the Kohn-Sham eigenvalues as written in OUTCAR and in EIGENVAL (or as plotted in the band structure), and take the difference of the energies of the lowest unoccupied state and the highest occupied state (please check each k-point carefully) The occupancies of each eigenstate are written in OUTCAR. Please mind that the VBM and the CBM usually are found at k-points at the edge of the BZ (Gamma, R,...) therefore, if you need accurate gap widths, please make sure that these k-points are included in your k-mesh.
1) have a look in DOSCAR: the DOS should drop to zero at the Fermi level if your system is insulating/semiconducting, the gap with can then be calculated from the energy differences between the bottom of the conduction band and the top of the valence band.
2) have a look at the Kohn-Sham eigenvalues as written in OUTCAR and in EIGENVAL (or as plotted in the band structure), and take the difference of the energies of the lowest unoccupied state and the highest occupied state (please check each k-point carefully) The occupancies of each eigenstate are written in OUTCAR. Please mind that the VBM and the CBM usually are found at k-points at the edge of the BZ (Gamma, R,...) therefore, if you need accurate gap widths, please make sure that these k-points are included in your k-mesh.
Last edited by admin on Tue Dec 11, 2007 12:51 pm, edited 1 time in total.