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.

• git clone https://github.com/Infant83/VASPBAUM.git

• 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

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

• 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)
  

  2. 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)
  

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

• Hyun-Jung Kim: Main developer ([email protected])

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