Bandgap of Si using different DFT+HF methods: Difference between revisions

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Description: Bandgap of Si using different DFT+HF schemes (PBE, B3LYP, PBE0, HSE06, and HF)
{{Template:Hybrid_functionals - Tutorial}}


----
== Task ==
*INCAR
<pre>
## Better preconverge with PBE first
## and use the WAVECAR file as inout for the DFT+HF calculation
 
## Selects the B3LYP hybrid function
#LHFCALC = .TRUE. ; GGA = B3 ; AEXX = 0.2 ; AGGAX = 0.72
#AGGAC = 0.81 ; ALDAC = 0.19
#ALGO = D ; TIME = 0.4
 
## Selects the PBE0  hybrid function
#LHFCALC = .TRUE. ;
#ALGO = D ; TIME = 0.4


## Selects the HSE06 hybrid function
Calculation of the band gap in Si using different DFT+HF schemes [[list_of_hybrid_functionals|(PBE, B3LYP, PBE0, HSE06, and HF)]].
#LHFCALC = .TRUE. ; HFSCREEN = 0.2 ;
#ALGO = D ; TIME = 0.4
 
## Selects HF  
#LHFCALC = .TRUE. ; AEXX = 1.0 ; ALDAC = 0.0 ; AGGAC = 0
#ALGO = D ; TIME = 0.4
 
## Leave this in
ISMEAR =  0
SIGMA  =  0.01
GGA    = PE
 
</pre>


*KPOINTS
== Input ==
<pre>
k-points
0
Gamma
  4  4  4
  0  0  0
</pre>


*POSCAR
=== {{TAG|POSCAR}} ===
<pre>
<pre>
System: Si                             
System: Si                             
Line 52: Line 19:
0.25 0.25 0.25
0.25 0.25 0.25
</pre>
</pre>
=== {{TAG|INCAR}} ===
## Better preconverge with PBE first
## and use the WAVECAR file as inout for the DFT+HF calculation
   
## Selects the B3LYP hybrid functional
#{{TAGBL|LHFCALC}} = .TRUE. ; {{TAGBL|GGA}} = B3 ; {{TAGBL|AEXX}} = 0.2 ; {{TAGBL|AGGAX}} = 0.72
#{{TAGBL|AGGAC}} = 0.81 ; {{TAGBL|ALDAC}} = 0.19
#{{TAGBL|ALGO}} = D ; {{TAGBL|TIME}} = 0.4
   
## Selects the PBE0  hybrid functional
#{{TAGBL|LHFCALC}} = .TRUE. ;
#{{TAGBL|ALGO}} = D ; {{TAGBL|TIME}} = 0.4
   
## Selects the HSE06 hybrid functional
#{{TAGBL|LHFCALC}} = .TRUE. ; {{TAGBL|HFSCREEN}} = 0.2 ;
#{{TAGBL|ALGO}} = D ; {{TAGBL|TIME}} = 0.4
   
## Selects HF
#{{TAGBL|LHFCALC}} = .TRUE. ; {{TAGBL|AEXX}} = 1.0 ; {{TAGBL|ALDAC}} = 0.0 ; {{TAGBL|AGGAC}} = 0
#{{TAGBL|ALGO}} = D ; {{TAGBL|TIME}} = 0.4
   
## Leave this in
{{TAGBL|ISMEAR}} =  0
{{TAGBL|SIGMA}}  =  0.01
{{TAGBL|GGA}}    = PE
=== {{TAG|KPOINTS}} ===
<pre>
k-points
0
Gamma
  6  6  6
  0  0  0
</pre>
=== Calculation ===


*script to extract eigenvalues and calculate the bandgap
*script to extract eigenvalues and calculate the bandgap
<pre>
<pre>
grep "      4    " OUTCAR | head -8 | \
homo=`awk '/NELECT/ {print $3/2}' $1`
awk 'BEGIN{i=1}{a[i]=$2 ; i=i+1} END{for (j=1;j<i;j++) print j,a[j]}' > vband.dat
lumo=`awk '/NELECT/ {print $3/2+1}' $1`
grep "     5     " OUTCAR | head -8 | \
nkpt=`awk '/NKPTS/ {print $4}' $1`
awk 'BEGIN{i=1}{a[i]=$2 ; i=i+1} END{for (j=1;j<i;j++) print j,a[j]}' > cband.dat
 
e1=`grep "     $homo     " $1 | head -$nkpt | sort -n -k 2 | tail -1 | awk '{print $2}'`
e2=`grep "    $lumo    " $1 | head -$nkpt | sort -n -k 2 | head -1 | awk '{print $2}'`
 
echo "HOMO: band:" $homo " E=" $e1
echo "LUMO: band:" $lumo " E=" $e2
</pre>
</pre>
:type
./gap.sh OUTCAR


*README.txt
*README.txt
Line 71: Line 85:
     bandgap = min(cband) - max(vband)  
     bandgap = min(cband) - max(vband)  
</pre>
</pre>


== Download ==
== Download ==
[http://www.vasp.at/vasp-workshop/examples/Si_hybrids_gap.tgz Si_hybrids_gap.tgz]
[[Media:Si hybrids gap.tgz| Si_hybrids_gap.tgz]]
{{Template:Hybrid_functionals}}


----
Back to the [[The_VASP_Manual|main page]].
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]


[[Category:Examples]]
[[Category:Examples]]

Latest revision as of 09:24, 6 April 2022

Task

Calculation of the band gap in Si using different DFT+HF schemes (PBE, B3LYP, PBE0, HSE06, and HF).

Input

POSCAR

System: Si                             
 5.430 
 0.5 0.5 0.0
 0.0 0.5 0.5
 0.5 0.0 0.5
   1  
Cartesian
0    0    0
0.25 0.25 0.25

INCAR

## Better preconverge with PBE first
## and use the WAVECAR file as inout for the DFT+HF calculation
   
## Selects the B3LYP hybrid functional
#LHFCALC = .TRUE. ; GGA = B3 ; AEXX = 0.2 ; AGGAX = 0.72 
#AGGAC = 0.81 ; ALDAC = 0.19
#ALGO = D ; TIME = 0.4 
   
## Selects the PBE0  hybrid functional
#LHFCALC = .TRUE. ; 
#ALGO = D ; TIME = 0.4 
   
## Selects the HSE06 hybrid functional
#LHFCALC = .TRUE. ; HFSCREEN = 0.2 ; 
#ALGO = D ; TIME = 0.4 
   
## Selects HF 
#LHFCALC = .TRUE. ; AEXX = 1.0 ; ALDAC = 0.0 ; AGGAC = 0
#ALGO = D ; TIME = 0.4 
   
## Leave this in
ISMEAR =  0
SIGMA  =  0.01
GGA    = PE

KPOINTS

k-points
0
Gamma
  6  6  6
  0  0  0

Calculation

  • script to extract eigenvalues and calculate the bandgap
homo=`awk '/NELECT/ {print $3/2}' $1`
lumo=`awk '/NELECT/ {print $3/2+1}' $1`
nkpt=`awk '/NKPTS/ {print $4}' $1`

e1=`grep "     $homo     " $1 | head -$nkpt | sort -n -k 2 | tail -1 | awk '{print $2}'`
e2=`grep "     $lumo     " $1 | head -$nkpt | sort -n -k 2 | head -1 | awk '{print $2}'`

echo "HOMO: band:" $homo " E=" $e1
echo "LUMO: band:" $lumo " E=" $e2
type
./gap.sh OUTCAR


  • README.txt
For each HF+DFT method (B3LYP, PBE0, HSE06, and HF) compute the bandgap of Si
adopting the following procedure:

i) Perform a standard PBE calculation
ii) Perform a HF+DFT run (VASP reads in the WAVECAR from run (i)
iii) Calculate the value of the bandgap by running the script 'gap': 
     bandgap = min(cband) - max(vband)

Download

Si_hybrids_gap.tgz

Back to the main page.

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