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<p>Dear Anindya,</p>
<p><i><font color="#3333ff">1.If the initial projection of a
material( suppose silicon with projection=sp3) doesn't give
the correct wannier band structure in such a situation what
should we do?</font></i></p>
<p>It very much depends on the material, e.g.
insulator/semiconductor or metal, the type of calculation you are
doing---simple wannierisation or
disentanglement+wannierisation---as well as convergence with
respect to the k-points grid. If you are interested in a specific
material, it'd be helpful if you could give us more information
about what you want to do and what you have tried so far. <br>
</p>
<p>Some obvious options are: 1) Try with random projections. 2) Try
the same initial projections but with a different orientation
(look at the user guide for details). 3) Modify the frozen and
outer energy windows (if any). 4) Try to converge with lower
thresholds. <br>
</p>
<p><i><font color="#3333ff">2.After relaxation, we can check the
relaxed coordinate of the atoms of our desired unit cell and
we can also find the fractional relaxed coordinate values of
atoms.Can we directly apply these fractional coordinate values
in the card proj(1),proj(2) etc and can put the orbital along
the coordinates?</font></i></p>
<p>This should be clear from the user_guide. You can specify any
fractional co-ordinate in the projection block and attach to it
any orbital in the list given in the user guide (chapter 3, pag
45-46). The syntax is:<br>
</p>
<p>begin projections<br>
f = frac_x , frac_y, frac_z: s (or p,d,sp3, etc.)<br>
.<br>
.<br>
end projections</p>
<p>where the letter "f" instructs the code you are going to specify
fractional co-odinates and frac_x, frac_y, frac_z are the actual
values of the x,y,z components of the relaxed co-ordinates of your
atom (or any other point in the unit cell). This is equivalent to
use the atom symbol (for example Si), if the atomic co-ordinates
in the atoms block are the relaxed ones. The syntax in this case
is:</p>
<p>begin projections<br>
Si:s (or p,sp3, etc.) <br>
end projections</p>
<i><font color="#3333ff">3.Is there any other method to compute the
correct projection of materials?<br>
</font></i>
<p>In the new release of the code there is going to be a new method
to compute the projections, which doesn't rely on initial guesses,
but we are still working to make it robust.</p>
<p>Best wishes,</p>
<p>Valerio<br>
</p>
<br>
<div class="moz-cite-prefix">On 23/08/18 12:59, Anindya Bose wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAJXtw3wwUtS9uVcLHOUoPZDDFdLMTHEQBFh7B5K-nwL+W84eeg@mail.gmail.com">
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Dear Experts,<br>
It is always a tough job to obtain correct wannier band structure
which is exactly similar with pw band structure.If wannierization
is correct,one should obtain correct band structure and band gap
also.To the best of my knowledge,convergence of band structure is
mostly depend on the projection.Now I would like to know;<br>
1.If the initial projection of a material( suppose silicon with
projection=sp3) doesn't give the correct wannier band structure in
such a situation what should we do?<br>
2.After relaxation, we can check the relaxed coordinate of the
atoms of our desired unit cell and we can also find the fractional
relaxed coordinate values of atoms.Can we directly apply these
fractional coordinate values in the card proj(1),proj(2) etc and
can put the orbital along the coordinates?<br>
Will it make the wannier band structure correct?<br>
3.Is there any other method to compute the correct projection of
materials?<br>
<br>
Thanks and regards,<br>
Anindya Bose<br>
Research Fellow,<br>
IIIT Allahabad<br>
<br>
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<br>
<pre class="moz-signature" cols="72">--
Postdoctoral research associate
Imperial College London
Exhibition road
London SW7 2AZ
and
TCM Group, Cavendish Laboratory
19 JJ Thomson Avenue
Cambridge</pre>
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