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. In this tutorial the modelBSE setup from the previous tutorial is used in combination with a $10 \times 10 \times 10$ gamma centered k-point grid (if you don't want to wait that long, a $4 \times 4 \times 4$ 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.

Download

Si_BSEfatbands.tgz

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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