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<div class="">Dear Wannier90 user,</div>
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<div class="">One of the conventions for the use of this mailing list is to sign with your name and affiliation in all posts, and we would all be very grateful if you would please adhere to this convention.</div>
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<div class="">Regarding your question below, it seems like your WFs may not be entirely real. If you plot them (wannier_plot = true), the code should report at the end of the .wout file whether the WFs have any significant imaginary part. </div>
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<div class="">Of course if you start the minimisation with an initial guess that is somewhat perverse (eg, with projection orbitals that have the wrong symmetry in comparison to what one expects to find) then the minimisation algorthim is going to have more
difficulty in finding the correct WFs.</div>
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<div class="">Best wishes,</div>
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<div class="">Arash</div>
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— <br class="">
Arash Mostofi — <a href="http://www.mostofigroup.org" class="">www.mostofigroup.org</a><br class="">
Director, CDT in Theory and Simulation of Materials<br class="">
Director, Thomas Young Centre @Imperial</div>
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Imperial College London</div>
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<div class="">On 1 May 2017, at 15:59, balabi <<a href="mailto:balabi@qq.com" class="">balabi@qq.com</a>> wrote:</div>
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<div class="">I am new to wannier90 and after some experiences with it, I found a problem.</div>
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<div class="">I am using wannier90-2.1.0. Take example05 diamond as an example.</div>
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<div class="">The example uses delicate initial projection</div>
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<div class="">f=0.0,0.0,0.0:s</div>
<div class="">f=0.0,0.0,0.5:s</div>
<div class="">f=0.0,0.5,0.0:s</div>
<div class="">f=0.5,0.0,0.0:s</div>
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<div class="">These are s orbitals located on center of C-C bond. I say the projection is delicate, because the spread is almost minimal even in the first iteration, so the convergence is fast. I use below convergence options</div>
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<div class="">conv_window = 10</div>
<div class="">conv_tol = 1.d-15</div>
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<div class="">the convergence is done in 74 steps. And examine hr.dat file, all imaginary part is zero.</div>
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<div class=""> -3 1 1 1 1 0.007379 0.000000</div>
<div class=""> -3 1 1 2 1 -0.008540 0.000000</div>
<div class=""> -3 1 1 3 1 -0.008540 0.000000</div>
<div class=""> -3 1 1 4 1 -0.008540 0.000000</div>
<div class=""> -3 1 1 1 2 -0.008540 -0.000000</div>
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<div class="">But as <a href="http://mailman.qe-forge.org/pipermail/wannier/2017-April/001350.html" class="">http://mailman.qe-forge.org/pipermail/wannier/2017-April/001350.html</a> says for non-entangle case, wannierisation is robust to initial projection.
As a test and for reproducibility, I choose below projection instead of random projection</div>
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<div class="">f=0.0,0.0,0.0:dxy</div>
<div class="">f=0.0,0.0,0.5:dxy</div>
<div class="">f=0.0,0.5,0.0:dxy</div>
<div class="">f=0.5,0.0,0.0:dxy</div>
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<div class="">conv_window and conv_tol are as previous. The convergence takes much more steps, totally 1168 steps. But the final state is the same to every digit in wout file, and xsf file visually the same in xcrysden</div>
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<div class="">Final State</div>
<div class=""> WF centre and spread 1 ( -0.806995, 0.806995, 0.000000 ) 0.58022874</div>
<div class=""> WF centre and spread 2 ( -0.000000, 0.000000, -0.000000 ) 0.58022873</div>
<div class=""> WF centre and spread 3 ( -0.806995, -0.000000, 0.806995 ) 0.58022875</div>
<div class=""> WF centre and spread 4 ( -0.000000, 0.806995, 0.806995 ) 0.58022873</div>
<div class=""> Sum of centres and spreads ( -1.613990, 1.613990, 1.613990 ) 2.32091495</div>
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<div class=""> Spreads (Ang^2) Omega I = 1.954626519</div>
<div class=""> ================ Omega D = 0.000000000</div>
<div class=""> Omega OD = 0.366288427</div>
<div class=""> Final Spread (Ang^2) Omega Total = 2.320914946</div>
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<div class="">However, if we look at the hr.dat this time. The content is as below</div>
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<div class=""> -3 1 1 1 1 0.007379 0.000000</div>
<div class=""> -3 1 1 2 1 -0.007476 0.004128</div>
<div class=""> -3 1 1 3 1 0.008130 -0.002616</div>
<div class=""> -3 1 1 4 1 0.008218 -0.002326</div>
<div class=""> -3 1 1 1 2 -0.007476 -0.004128</div>
<div class=""> -3 1 1 2 2 0.007379 0.000000</div>
<div class=""> -3 1 1 3 2 0.008382 0.001639</div>
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<div class="">I really don't understand why such a significant imaginary parts considering that we have exactly the same wannierisation result？ Besides, I've tried many random projection all get same wannierisation, but failed to get even one clean hr.dat with
zero imaginary part.</div>
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