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 ==== I obtain negative occupations. Is that wrong? ====
-No. This occurs normally for the tetrahedron method using the corrections from  [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]]. It reflects that the Brillouin-zone integration is not approximated by a sampling over a discrete k-point set, but energies and matrix elements are interpolated in between. What is printed as occupations are actually integration weights, which include the interpolation between the discrete k-points. Using these elaborate integration weights, the integral of the interpolated matrix elements and energies can still be expressed as weighted sum over the discrete k-point set. The interpolation is effectively "hidden" from the user at a price that the weights have a complicated form and take on values that appear, at first sight, unphysical. When the interpolation between the discrete k-points is non-linear, which is the case with the "correction formula" from [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]], the integration weights may also be negative or be larger than one. See for example Eq.22 and Fig.7 of [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]].
+No. This occurs normally for the tetrahedron method using the corrections from  [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]]. It reflects that the Brillouin-zone integration is not approximated by a sampling over a discrete k-point set, but energies and matrix elements are interpolated in between. What is printed as occupations are actually integration weights, which include the interpolation between the discrete k-points. Using these elaborate integration weights, the integral of the interpolated matrix elements and energies can still be expressed as weighted sum over the discrete k-point set. The interpolation is effectively "hidden" from the user at a price that the weights have a complicated form and take on values that appear, at first sight, unphysical. When the interpolation between the discrete k-points is non-linear, which is the case with the "correction formula" from [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]], the integration weights may also be negative or larger than one. See for example Eq.22 and Fig.7 of [[https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223|Blöchl et al. Phys. Rev. B 49, 16223 (1994)]].