Dear Will,
the quantities computed by the code are presented in Phys. Rev. B 85,
085201 (2012).
More precisely, you can collect the quantity in Eq. 8 (detailed in
Appendix A) for the k points specified in input. Roughly speaking, that
is the amount unfolded states with equivalent k vector contribute to the
folded state at a given energy. Admittedly this is far from clear but
the article mentioned above describes very accurately both the problem
and the proposed solution. Still I hope that my awkward description will
be sufficient to understand that, in a perfect supercell, this number
depends on the degeneracy of the eigenvalue in the base cell. If the
symmetry is low enough (and forgetting about spin), this number is
either 0 or 1.
The picture that you are sharing is actually Eq. 9, which is the
quantity described above times a Dirac delta function of the energy,
which is approximated with a Gaussian.
As a consequence, the 'weight' in a perfect supercell depends on the
degeneracy (or almost degeneracy) of a state, the discretization of the
energy interval and the width of the Gaussian approximating the Dirac delta.
I hope this partially answers your question.
That being said, as you may have read, I've been always advocating for
bandUP, since unfold.x was just my exercise to learn Fortran and the
internals of QE.
However, lately I found a little bit of time to fix some problems, add
some tests and parallel execution, so I'm a little more confident than
before on its correctness. Still let me remind you to carefully check
your results and feel free to contact me for further details.
Best regards,
Pietro
--
Pietro Bonfà
Department of Mathematical, Physical and Computer Sciences
University of Parma
On 1/3/21 5:37 AM, William Hewett wrote:
Hi all,
I'm using QE to calculate the band structure of rare-earth nitride
materials, currently looking at the effect of nitrogen vacancies and the
resulting states created. I'm running calculations on 3x3x3 (primitive)
supercells, then using unfold.x to process the results.
Unfold.x gives an output where each point (k,energy) also has a 'weight'
clearly this is zero where no states are present and non-zero where they
are present. My question is, what exactly is this weight? Some sort of
DOS for a single k-point?
i.e. in the image below most points in the VB (near 6 on the y-axis) are
quite dark, while some points in the CB (flat 4f bands near -1) are
lighter in color.
image.png
Kind regards,
Will Hewett
Post Doctoral Researcher
Victoria University of Wellington
New Zealand
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_______________________________________________
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users mailing list [email protected]
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