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exercises:2014_ethz_mmm:bs [2014/05/20 08:18]
pshinde
exercises:2014_ethz_mmm:bs [2014/10/15 13:35] (current)
oschuett
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    $ module load espresso/​5.0.2_openmpi    $ module load espresso/​5.0.2_openmpi
  
-2. Create a new directory and copy all the files from /​cluster/​home03/​stud/​pshinde/​Graphene/ ​  to the newly created directory.+2. Create a new directory and download ​all the **commented** ​files from the media manager: {{exercise_11.2.tar.gz|}},​ copying them to the newly created directory.
  
 **Self-Consistent Field (SCF) calculation:​** **Self-Consistent Field (SCF) calculation:​**
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    $ grep “Fermi energy” ​ SCF.out | tail -1    $ grep “Fermi energy” ​ SCF.out | tail -1
  
-10For density of states ​calculation, ​we need dense k-grid. Therefore, do the non-self-consistent calculation using the input file "​nscf.in"​ (Please do not change the k-grid ​in nscf.in)+6. Copy the mol.save directory to scf-mol.save. The scf-mol.save is required for '​bands'​ calculation 
 +   $ cp -rf mol.save/ scf-mol.save/​ 
 + 
 +**Non-Self-Consistent Field (NSCF) calculation:​** 
 + 
 +In non-self-consistent calculation,​ the potential is constructed from some “input” charge ​density ​and remains fixed. Calculation ​of DOS can be done in two ways: 
 + 
 +a) For finite geometries (e.g. molecules), where a single k-point (centre of BZ) is sufficient, the simple way is to perform self-consistent ​calculation ​and then DOS calculation. 
 + 
 +b) For periodic geometriesa high quality DOS might require very fine meshes and for large cells one might need many k-points (depending on the system). Therefore, to save the computational time it is a good idea to calculate the self-consistent charge density with few k-points and then non-self-consistent calculation using fixed self-consistent charge density. 
 + 
 +7. For density of states calculation, do the non-self-consistent calculation using the input file "​nscf.in"​ (change the k-grid ​KX KY KZ) and prefix = '​./​mol'​.
    $ bsub -n 4 " mpirun pw.x < nscf.in > NSCF.out "    $ bsub -n 4 " mpirun pw.x < nscf.in > NSCF.out "
    
-11At the end, use dos.in input file to get the density of states from -20 to 10 eV. First column of "​graphene.dos"​ file is the energy and second column is the total DOS. Open plot_dos.plt script to add Fermi energy and save the plot using gnu plot.+8and then use dos.in input file to get the density of states from -20 to 10 eV.
    $ bsub -n 4 " mpirun dos.x < dos.in > DOS.out "    $ bsub -n 4 " mpirun dos.x < dos.in > DOS.out "
-6. For band structure calculation,​ use the input file '​bands.in'​ and the ground-state density obtained from the '​scf'​ run (prefix = '​./​mol'​). The BZ for graphene is shown in figure below. The points Γ, K and M are called the zone centre, the corner and the centre of the edge respectively. The green lines show the borders of the irreducible BZ along which the band extrema occurs. Therefore, we move along these lines to get the energy that an electron can have within the solid. Now the k-grid is replaced with a list of high-symmetry points along Γ-M-K-Γ directions. You can run the kpoints program and get a list of kpoints along the high-symmetry lines. For this you need to compile the kpoints.c program using gcc compiler+First column of "​graphene.dos"​ file is the energy and second column is the total DOS. Open plot_dos.plt script to add Fermi energy and save the plot using gnu plot. The DOS should look like this, 
 + 
 +{{ graphene_dos.png?​500 | }} 
 + 
 +9. For band structure calculation,​ use the input file '​bands.in'​ and the ground-state density obtained from the '​scf'​ run (prefix = './scf-mol'). The BZ for graphene is shown in figure below. The points Γ, K and M are called the zone centre, the corner and the centre of the edge respectively. The green lines show the borders of the irreducible BZ along which the band extrema occurs. Therefore, we move along these lines to get the energy that an electron can have within the solid. Now the k-grid is replaced with a list of high-symmetry points along Γ-M-K-Γ directions. You can run the kpoints program and get a list of kpoints along the high-symmetry lines. For this you need to compile the kpoints.c program using gcc compiler
  
-{{ : exercise:Graphene-BZ.png?​500 | }} +{{ Graphene-BZ.png?​500 | }} 
  
    $ gcc –Wall kpoints.c –o kpoints    $ gcc –Wall kpoints.c –o kpoints
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    $ bsub -n 4 " mpirun pw.x < bands.in > BANDS.out "    $ bsub -n 4 " mpirun pw.x < bands.in > BANDS.out "
  
-7. Ones the job is over, arrange the band energies according to the number of k-points. This means you need to write the data (from BANDS.out)+10. Ones the job is over, arrange the band energies according to the number of k-points. This means you need to write the data (from BANDS.out)
  
           k = 0.0000 0.0000 0.0000 ​    band energies (ev):           k = 0.0000 0.0000 0.0000 ​    band energies (ev):
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        ​N ​       EN (KN)        ​N ​       EN (KN)
  
-8.   Use Qe_Bands.sh script to do this job+11.   Use Qe_Bands.sh script to do this job
  
    $ bash Qe_Bands.sh BANDS.out <​FermiEnergy>​    $ bash Qe_Bands.sh BANDS.out <​FermiEnergy>​
  
-9.   Plot (column 1 Vs column 2 of EnergyValues.txt) and save the band structure using gnu plot. Compare your band structure with the image provided here. The Fermi energy is set to zero. Do you see the linear dispersion of bands at K-point (+- 1 eV around the Fermi energy)?+12.   Plot (column 1 Vs column 2 of EnergyValues.txt) and save the band structure using gnu plot. Compare your band structure with the image provided here. The Fermi energy is set to zero. Do you see the linear dispersion of bands at K-point (+- 1 eV around the Fermi energy)?
  
    $ gnuplot plot_band.plt    $ gnuplot plot_band.plt
  
-{{ : exercise:Graphene-bands-reference.png?​500 | }} +{{ Graphene-bands-reference.png?​500 | }} 
  
-    
-{{ : exercise:​graphene_dos.png?​500 | }} 
  
 +13.  Before going for the different k-grid please delete all mol.save directories.
 +    $ rm -rf mol.save/
 +    $ rm -rf scf-mol.save/​
  
  
exercises/2014_ethz_mmm/bs.1400573923.txt.gz · Last modified: 2014/05/20 08:18 by pshinde