1. Structural optimization (primitive cell of diamond)

Please prepare the following files except the POTCAR (using vpot.py)

  • INCAR:

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    System = relax_diamond
    PREC = N
    ENCUT = 500
    EDIFF = 1e-4
    EDIFFG = -0.01
    IBRION = 2
    ISIF = 3
    NSW = 100
    NPAR = 4
    ISMEAR = 0
    SIGMA = 0.05
    LCHARG = F
    LWAVE = F

  • POSCAR:

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    primitive cell-Diamond
    1.0
            2.5269939899         0.0000000000         0.0000000000
            1.2634969950         2.1884409905         0.0000000000
            1.2634969950         0.7294803302         2.0632819528
        C
        2
    Direct
         0.249999998         0.249999996         0.250000007
         0.000000000         0.000000000         0.000000000

  • KPOINTS:

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    K-points
    0
    M
    11  11  11
     0 0 0

  • Use the vpot.py script to generate files automatically

After sufficient structural optimization, you will get the final structure in CONTCAR

  • CONTCAR:

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    primitive cell-Diamond
       1.00000000000000
         2.5250599384000001    0.0000000000000000    0.0000000000000000
         1.2625299692000000    2.1867660527999999    0.0000000000000000
         1.2625299692000000    0.7289220176000000    2.0617028064000000
       C
         2
    Direct
      0.2500000000000000  0.2500000000000000  0.2500000000000000
      0.0000000000000000  0.0000000000000000  0.0000000000000000

  • Next, save the CONTCAR as POSCAR file

2. Pre-process

Create a new folder (phon) for phonon spectrum calculations
Four files need to be prepared：POSCAR、INCAR、POTCAR、and KPOINTS

  • INCAR:

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    System = phonon_diamond
    PREC = N
    ENCUT = 500
    IBRION = 8 
    EDIFF = 1.0e-08  
    ISMEAR = 0 
    SIGMA = 0.1
    LREAL = .FALSE. 
    ADDGRID = .TRUE.
    LWAVE = .FALSE. 
    LCHARG = .FALSE.

  • First, import the run environment

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    module load phonopy/1.11.10.4

In the pre-process, supercell structures with (or without) displacements are created from a unit cell fully consiering crystal symmetry.

  • To obtain supercells (2 × 2 × 2) with displacements, run phonopy:

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    phonopy -d --dim="2 2 2"

  • You should find the files, SPOSCAR, disp.yaml, and POSCAR-{number} as follows:

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    INCAR  KPOINTS  POSCAR  POSCAR-001  POTCAR  SPOSCAR  disp.yaml  phonopy_disp.yaml

  • SPOSCAR is the perfect supercell structure, disp.yaml contains the information on displacements, and POSCAR-{number} are the supercells with atomic displacements. POSCAR-{number} corresponds to the different atomic displacements written in disp.yaml.

3. Calculation of sets of forces

  • Save the primitive cell of diamond to primitive

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    % cp POSCAR primitive

  • Rename SPOSCAR created in (2) to POSCAR (POSCAR-{number} and disp.yaml files will never be used.)

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    % mv SPOSCAR POSCAR

4. Submit computational task

  • After finishing the VASP calculation, confirm vasprun.xml contains hessian elements, and then create FORCE_CONSTANTS, enter the following command in terminal

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    % phonopy --fc vasprun.xml

  • You will see the following

5. Prepare the following setting file named with band.conf

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ATOM_NAME = C
FORCE_CONSTANTS = READ 
DIM = 2 2 2 
BAND =   0  0  0  0.5 0  0.5 0.625 0.25 0.625 0.375 0.375 0.75 0  0  0  0.5 0.5 0.5  0.5 0.25 0.75 0  0  0   
MP =  8 8 8
PDOS = 1

6. Run phonopy with the original unit cell POSCAR-unitcell and setting tag FORCE_CONSTANTS = READ

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% phonopy --dim="2 2 2" -c primitive band.conf
# or
% phonopy -c primitive -p band.conf --factor=521.471
  • You will see the following
  • Phonon partial density of states data is located in partial_dos.dat

7. Export the original data file named with band.dat

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bandplot --gnuplot band.yaml >band.dat