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VASPBAUM

BAnd Unfolding Machinery for VASP output (VASP-BAUM). VASPBAUM is written for the post-processing purpose of the VASP outputs, i.e., WAVECAR the Bloch wavefunction information. VASPBAUM can compute band structure unfolding via k-projection method [See described in Phys. Rev. B 85, 085201 (2012).] In addition Circular dichroism also can be evaluated.

Download git version

Compile

  • Serial version : set MPI_USE = NO in makefile

    make vaspbaum.serial or make

  • Multicore version : set MPI_USE = YES in makefile

    make vaspbaum.mpi or make

Features

  • Band structure unfolding along primitive unit cell brillouin zone k-path
  • Circular dichroism (optical selectivity response to the circulary polarized light)

Usage

  • Instruction and possible options

./vaspbaum.mpi -h

  • generate supercell K-point that primitive k-point along high symmetry path is folded into.

    1. Prepare KPOINTS_PC : k-point path of primitive Brillouin zone (BZ) that to be unfolded onto
    2. Prepare POSCAR_PC : primitive cell lattice information (VASP POSCAR format)
    3. Prepare POSCAR_SC : Super cell lattice information (VASP POSCAR format)
    4. run "vaspbaum" : vaspbaum -set_unfold
    5. KPOINTS_SC file will be generated --> copy KPOINTS_SC into KPOINTS to calculate WAVECAR
  • run unfolding

    1. Once you generated "WAVECAR" with KPOINTS_SC
    2. run "vaspbaum" to unfold:

    vaspbaum -unfold -nosoc -sigma 0.10 -nediv 4000 -norm T -ef -1.2

      -nosoc : without SOC (if SOC, set -soc) 
      -nediv : division of energy window for spectral function 
      -norm  : normalize wavefunction 
      -ef    : set Fermi level       
      -sigma : full width at half maximum for the Lorenztian line shape function 
      	   (used for smearing of spectral function) 
    
  • run unfolding with circular dichroism (same with "unfolding" functionality but include cicularly polarization)

    1. run "vaspbaum" :

    vaspbaum -unfold -nosoc -sigma 0.10 -nediv 4000 -norm T -cd 2 -ien 0.0 -fen 4.0

      -ien   : incident photon energy (minimum) 
      -fen   : incident photon energy (maximum)
    
    1. You can also control the angle of incident photon with respect to the surface by -theta and -phi tag

    vaspbaum.mpi -unfold -nosoc -sigma 0.10 -nediv 4000 -norm T -cd 2 -ien 0.0 -fen 4.0 -theta 65.0

      -theta : angle along z-axis describing the direction of the injecting light 
      -phi   : angle along x-axis describing the direction of the injecting light
      
      - Example:
      	-Light from z-axis(surface normal): (theta,phi) = (0.0,0.0)
      	-Light from x-axis                : (theta,phi) = (90.0,0.0)
      	-Light from y-axis                : (theta,phi) = (90.0,90.0)
    

Example

  • WSe2 twisted bilayer system (The example for unfold with CD is provided upon reasonable request)

Contributors

Citation of the code:

  • The code is under active development. Please contact author ([email protected]) for the usage.