Plotting the BSE fatband structure of Si
Overview > Dielectric properties of Si using BSE > Improving the dielectric function > Plotting the BSE fatband structure of Si > List of tutorials
Task
Visualization of BSE eigenvectors using fatbands.
Input
Si 5.4300 0.5 0.5 0.0 0.0 0.5 0.5 0.5 0.0 0.5 2 cart 0.00 0.00 0.00 0.25 0.25 0.25
INCAR
- This is the INCAR file for the basic DFT calculation:
System = Si PREC = Normal ; ENCUT = 250.0 ISMEAR = 0 ; SIGMA = 0.01 KPAR = 2 EDIFF = 1.E-8 NBANDS = 16 LOPTICS = .TRUE. # needed for WAVEDER file LPEAD = .TRUE. OMEGAMAX = 40
KPOINTS
The KPOINTS file will be automatically generated in this example.
Calculation
- In this example we will calculate and plot the first "bright" BSE eigenstates of silicon, also called fatbands[1]. In this tutorial the modelBSE setup from the previous tutorial is used in combination with a gamma centered k-point grid (if you don't want to wait that long, a grid takes only a minute). In principle the standard BSE method can also be used instead.
= Step 1 DFT calculation
We run a standard DFT calculation with the input files given above.
Step 2 BSE calculation with fatbands
- The INCAR file for the modelBSE calculation looks like the following:
System = Si PREC = Normal ; ENCUT = 250.0 #ALGO = BSE ANTIRES = 0 ISMEAR = 0 ; SIGMA = 0.01 ENCUTGW = 150 EDIFF = 1.E-8 # default 1.E-4 NBANDS = 16 # only bands that are used are required, prepare the same set in a forgoing DFT run NBANDSO = 4 NBANDSV = 8 OMEGAMAX = 20 PRECFOCK = Normal ALGO = TDHF LMODELHF = .TRUE. #Turn model on HFSCREEN = 1.26 # Screening lenght AEXX = 0.088 #Inverse of epsilon_infinity SCISSOR = 0.69 # Difference GW-DFT band gap NBSEEIG = 10 # number of BSE eigenvectors written out in BSEFATBAND
- The important tag for fatband calculations is NBSEEIG. In this example this will write the 10 energetically lowest BSE eigenvectors to the output file BSEFATBAND.
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References
Overview > Dielectric properties of Si using BSE > Improving the dielectric function > Plotting the BSE fatband structure of Si > List of tutorials
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