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Difference between revisions of "Plotting the BSE fatband structure of Si"

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== Calculation ==  
 
== Calculation ==  
  
*In this example we will calculate and plot the first "bright" BSE eigenstate of silicon. In this tutorial the modelBSE setup from the previous tutorial is used in combination with a <math>10 \times 10 \times 10</math> gamma centered k-point grid (if you don't want to wait that long, a <math> 4 \times 4 \times 4</math> grid takes only a minute). In principle the standard BSE method can also be used instead.  
+
*In this example we will calculate and plot the first "bright" BSE eigenstates of silicon, also called fatbands<ref name="bokdam:scr:6"/>. In this tutorial the modelBSE setup from the previous tutorial is used in combination with a <math>10 \times 10 \times 10</math> gamma centered k-point grid (if you don't want to wait that long, a <math> 4 \times 4 \times 4</math> grid takes only a minute). In principle the standard BSE method can also be used instead.  
 
*The {{TAG|INCAR}} file for the modelBSE calculation looks like the following:
 
*The {{TAG|INCAR}} file for the modelBSE calculation looks like the following:
 
  {{TAGBL|System}}  = Si
 
  {{TAGBL|System}}  = Si

Revision as of 13:56, 14 December 2017

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.
  • 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


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