Solution LAB1 bands DOS diamond: Difference between revisions
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* Back to the previous page: [[Structural and electronic properties of semiconductors and metals #Convergences]] | * Back to the previous page: [[Structural and electronic properties of semiconductors and metals #Convergences]] | ||
=== | === Preliminaries === | ||
Given the calculations run previously to determine the converged set of k-points, ecutwfc, and lattice parameter, here we set the following: | Given the calculations run previously to determine the converged set of k-points, ecutwfc, and lattice parameter, here we set the following: | ||
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* The use of <code>mpirun -np 2</code> in the example above makes the calculation running on two MPI processes. | * The use of <code>mpirun -np 2</code> in the example above makes the calculation running on two MPI processes. | ||
=== DOS of Diamond === | |||
We start by addressing the '''calculation of the DOS'''. | We start by addressing the '''calculation of the DOS'''. | ||
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[[File:Dos_diamond.jpg | 450px| DOS of Diamond for different values of gaussian broadening.]] | [[File:Dos_diamond.jpg | 450px| DOS of Diamond for different values of gaussian broadening.]] | ||
=== Band structure of Diamond === | |||
Revision as of 09:49, 16 December 2020
- Back to the previous page: Structural and electronic properties of semiconductors and metals #Convergences
Preliminaries
Given the calculations run previously to determine the converged set of k-points, ecutwfc, and lattice parameter, here we set the following:
nk = 8 ecutwfc = 60.0 # could be lowered further alat = 6.6694212
As a preliminary step:
- make a new directory, e.g. called Diamond_BANDS
- In a situation like this it is always a good idea to start over from scratch with a fresh scf calculation.
- prepare an input file for a single scf run according to the parameters above.
&CONTROL
calculation="scf"
[...]
/
&SYSTEM
alat=...
ecutwfc=...
/
[...]
K_POINTS {automatic}
8 8 8 0 0 0
- run the calculation as:
mpirun -np 2 pw.x < scf.in > scf.out
- The use of
mpirun -np 2in the example above makes the calculation running on two MPI processes.
DOS of Diamond
We start by addressing the calculation of the DOS.
We need now to write the input file for a non-self consistent calculation using a regular k-point grid. The input file looks like:
>$ cat nscf_dos.in
&CONTROL
calculation="nscf"
verbosity="high" # not strictly needed but useful sometimes
[...]
/
&SYSTEM
alat=...
ecutwfc=...
nbnd=20 # let's include some empty states
/
[...]
K_POINTS {automatic}
20 20 20 0 0 0 # here we use a much denser kpt grid
Then we run it
mpirun -np 2 pw.x < nscf_dos.in > nscf_dos.out
Given the number of k-points requested, the calculation may take some time.
At this point we can prepare an input file for the dos.x program,
$> cat dos.in
&DOS
prefix = 'diamond'
outdir = './SCRATCH/'
degauss=0.025 ! [Ry] broadening parameter
fildos = 'dos_diamond_0.025Ry.dat'
/
The variable degauss controls the gaussian broadening used to approximate
Dirac delta's in the calculation.
Try to change this value to get a feeling of the effect is has on the computed DOS.
An example is show in the figure below.
