Tutorial

In the example, we provide the instructions and files needed to calculate carrier mobility limited by S-vacancy of MoS2. After downloading the package, the files could be found in example folder.

Setup

This example consists of the input files for QE to generate the wavefunction and the perturbation potential modelling a S-vacancy of MoS2 in a 6-by-6 supercell. The obtained files could then be used to calculate the e-d interaction matrix elements with EDI. Further instructions are then provided to obtain the carrier mobility limited defect.

When running the example, first follow the instructions in the Installation section and compile pw.x, pp.x, and edi.x. Assume they are located in $BIN folder, then copy the files in the example to a working directory to perform the calculation.

DFT calculation

  1. Scf calculation to obtain the perturbation potential:

    Use the input files pristine.scf.in and defect.scf.in to perform scf calculations for the pristine and defect structures.

$ mpirun -np $N $BIN/pw.x <prinstine.scf.in  >prinstine.scf.out

$ mpirun -np $N $BIN/pw.x <defect.scf.in     >defect.scf.out

  1. Postprocessing to generate the files of the perturbation potential:

    Use the input files pristine.pp.in and defect.pp.in to generate potential data files for the pristine and defect structures.

$ mpirun -np $N $BIN/pp.x <prinstine.pp.in  >prinstine.pp.out

$ mpirun -np $N $BIN/pp.x <defect.pp.in     >defect.pp.out

EDI preprocessing

  1. Calculate the band structure for full k grid

    Use the input files unitcell.scf.in, unitcell.w90.in to generate a coarse grid band structure.

$ mpirun -np $N $BIN/pw.x <unitcell.scf.in  >unitcell.scf.out

$ mpirun -np $N $BIN/pw.x <unitcell.w90.in  >unitcell.w90.out

Use the input files w90_mos2.win, pw2w90.in to generate a fine grid band structure. This example is using wannier90.x, assuming under the same directory $BIN.

$ mpirun -np $N $BIN/wannier90.x -pp w90_mos2

$ mpirun -np $N $BIN/pw2wannier90.x <pw2w90.in >pw2w90.out

$ mpirun -np $N $BIN/wannier90.x     w90_mos2

$ mpirun -np $N $BIN/postw90.x     w90_mos2

The generated velocity file w90_mos2_geninterp.dat is needed for next step.

  1. Generate the needed k points for e-d interaction matrix elements with triangular integral method

    Use the script wmat_mos2.py to obtain a list of k points in file kpt.dat, and a list of k point pairs to calculate the e-d interaction matrix element together with the weight wt.dat.

$ python wmat_mos2.py

Prepare the input files for nscf calculation with the data from kpt.dat file. This resulted file is provided as unitcell.nscf.in.

EDI calculation

  1. Generate the wavefunctions for the needed k points

    Use the input files unitcell.scf.in and unitcell.nscf.in to generate wavefunctions with proper k points.

$ mpirun -np $N $BIN/pw.x         <unitcell.scf.in  >unitcell.scf.out

$ mpirun -np $N $BIN/pw.x -nk $NK <unitcell.nscf.in  >unitcell.nscf.out

  1. Calculate e-d interaction matrix element

    Use the input files calcmdefect.dat and prepared weight file wt.dat to perform matrix element calculation with edi.x.

$ mpirun -np $N $BIN/edi.x -ni $N  >output

Mobility calculation

  1. Use MRTA model to calcualted the carrier mobility

    Previous calculation gives pp.dat file, use this file and the postprocessing script mu.py to calculate the carrier mobility.

$ python mu.py

This step will generate an output file containing the mobility, as well as the scattering rate which is ready to be plot.