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exercises:2014_ethz_mmm:bs [2014/05/22 13:03]
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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 **Non-Self-Consistent Field (NSCF) calculation:​** **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. 
  
-1) 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.+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:
  
-2) For periodic ​geometries, a high quality DOS might require very fine meshes and for large cells one might need many k-points ​(depending on the system). Thereforeto 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.+a) For finite ​geometries ​(e.g. molecules)where single ​k-point (centre of BZis sufficient, the simple way is to perform ​self-consistent ​calculation ​and then DOS calculation.
  
-7. For density of states calculationwe need dense k-grid. Therefore, do the non-self-consistent calculation using the input file "​nscf.in"​ (change the k-grid KX KY KZ) and prefix = '​./​mol'​.+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 "
    
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 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, 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,
  
-{{ : exercise:graphene_dos.png?​500 | }}+{{ 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 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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    $ gnuplot plot_band.plt    $ gnuplot plot_band.plt
  
-{{ : exercise:Graphene-bands-reference.png?​500 | }} +{{ Graphene-bands-reference.png?​500 | }} 
  
  
exercises/2014_ethz_mmm/bs.1400763792.txt.gz · Last modified: 2014/05/22 13:03 by pshinde