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Paulo V C Medeiros edited this page Jan 30, 2015
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BandUP -- Band Unfolding code for Plane-wave based calculations -- is a tool to obtain a primitive cell representation of the band structure of systems simulated using supercells. The unfolding of the bands is performed as described in the following papers:
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Paulo V. C. Medeiros, Sven Stafström and Jonas Björk, Phys. Rev. B 89, 041407(R) (2014)
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Paulo V. C. Medeiros, Stepan S. Tsirkin, Sven Stafström and Jonas Björk, Phys. Rev. B 91, 041116(R) (2015)
The current version of BandUP can be used as a standalone post-processing band unfolding tool for calculations performed using VASP or Quantum ESPRESSO. Don't hesitate to contact us if you use other plane-wave code and you would like to have support to it added too. As usual, we'll do our best to help you out. This, of course, will be faster if you can collaborate with us. For instance, if you write and/or send us a routine to read the wavefunctions produced by your code, then we'd only need to write an interface to it.
No explicit calculations involving the reference primitive cell are needed, as the spectral weights used for the unfolding can be obtained entirely from some selected coefficients of the plane-waves that span the supercell eigenstates (see [Phys. Rev. B 85, 085201 (2012)](http://dx.doi.org/10.1103/PhysRevB.85.085201) and [Phys. Rev. B 91, 041116(R) (2015)](http://dx.doi.org/10.1103/PhysRevB.91.041116)). One only needs to know the primitive cell vectors to determine the geometric unfolding relations.
BandUP checks the symmetries of both supercell and reference primitive cell in order to (i) reduce the number of necessary k-points to a minimum — thus reducing the size of the WAVECAR file, and (ii) produce properly symmetry-averaged effective unfolded band structures (EBS) when the symmetry of the supercell is different from the one of the primitive cell. This is handy when defects, impurities and/or other types of perturbations are present. BandUP also comes with additional pre- and post-processing utilities to help you (i) choose the set of K-points that should be used with your electronic structure code to obtain the wavefunctions needed for band unfolding, (ii) plot the EBS, and (iii) obtain the smearing widths of the unfolded bands.