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<font size="4" class="">Dear QE Community,</font>
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<div class=""><font size="4" class="">We know that |psi(k,r)> =u(r)exp(ik.r), where u(r) has the periodicity of the lattice. The index k includes band index as well.</font></div>
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<div class=""><font size="4" class="">I would like to calculate the overlap integral u*_k’(r)u_k(r)d^3r. To this end, I have extracted the real and imaginary parts of </font></div>
<div class=""><font size="4" class="">wave function coefficients from evc.dat for all the k-points and bands by setting wf_collect=.true.</font><span style="font-size: large;" class="">.</span></div>
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<div class=""><font size="4" class="">I have two questions:</font></div>
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<div class=""><font size="4" class="">1. Am I correct in assuming that the above integral is equivalent to the sum(C*_k C_k’), where C’s are the coefficients from evc.dat and the sum is </font></div>
<div class=""><font size="4" class="">over igwx (maximum G-vector index) specified in eve.dat? </font></div>
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<div class=""><font size="4" class="">2. igwx is different for different k-points. One k-point may have igwx=1459 while another k-point has igwx=1468. In the above sum, is it correct to </font></div>
<div class=""><font size="4" class="">to use the top 1468 coefficients of the first k-point to calculate the overlap integral between the two k-points?</font></div>
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<div class=""><font size="4" class="">An earlier post (<a href="http://qe-forge.org/pipermail/pw_forum/2015-April/106663.html" class="">http://qe-forge.org/pipermail/pw_forum/2015-April/106663.html</a>) suggests a similar concept for <psi_i|psi_j> but not
for <u_i|u_j>.</font></div>
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<div class=""><font size="4" class="">Thank you,</font></div>
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<div class=""><font size="4" class="">Vahid</font></div>
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<div class=""><font size="4" class="">Vahid Askarpour<br class="">
Department of Physics and Atmospheric Science<br class="">
Dalhousie University,<br class="">
Halifax, NS, Canada<br class="">
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