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<p>Dear Wannier90 developer and users,</p>
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<p>I want to calculate overlaps of the periodic functions <u_nk|u_nk'> , where k is fixed and k' runs over the whole first Brillouin zone of a 2D material to compare with a tight binding model. Only a single band is considered. I generated a k-point grid using kmesh.pl, run scf, nscf calculations in Quantum Esrpresso and did wannier90 preprocessing.</p>
<p>To run pw2wannier I generated pairs of k-points entering the nnkpts block so that they include couplings between all k-points form the first BZ with each other (b-vector was always 0):</p>
<p><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">begin nnkpts<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">N*N<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">1 1 0 0 0<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">1 2 0 0 0<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">...<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">1 N 0 0 0<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">...<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">...<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">N 1 0 0 0<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">....<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">N N 0 0 0<br /></span><span style="font-family: 'courier new', courier, monospace; font-size: 10pt;">end nnkpts</span></p>
<p>where N is the numer of kpoints in FBZ. When I plot the overlaps |<u_nk| u_nk'>|^2 file in the FBZ, where k is fixed and k' runs over the whole BZ, the picture I get is not periodic, that is, when I replicate the BZ in kx and ky dimensions the full picture does not look like a smooth varying function but has step-like sharp changes at the border of BZ that do not fit each other. In contrast, the tight-binding model gives a periodic image. </p>
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<div>Shall I sum contributions |<u_nk| u_nk'(b) >|^2 of all b_k vectors from all shells to get the periodic image?<br />I would appreciate your help on this question.</div>
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<div>Best regards, </div>
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<div>Marcin Kurpas<br /> Institute of Physics<br /> University of Silesia in Katowice<br /><br /></div>
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