<div dir="ltr"><div>Dear Prof. Giovanni,<br><br></div>Thank you very much for your help. I do need to see how conductivity changes across the
three cases I mentioned under T=2K. But I should be satisfied with the
trend of change if the results look reasonable at higher T. I have
submitted jobs for T=50K and see how they will work out (still not finished yet). <br><div><br></div><div>Could
you please elaborate on what you mean by numerical and convergence
issues? I think I should have at least reached K-points and ENCUT
convergence.<br><br></div><div>Thanks,<br><br></div><div>Sincerely,<br></div>Jun</div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jun 15, 2017 at 12:24 PM, Giovanni Pizzi <span dir="ltr"><<a href="mailto:giovanni.pizzi@epfl.ch" target="_blank">giovanni.pizzi@epfl.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">
Dear Jun,
<div>You are working in the range of temperatures 2-10 K. Is this expected? Such low temperatures are very hard to work with in the code, because of numerical and convergence issues.</div>
<div><br>
</div>
<div>If you work at higher temperature, is the result better?</div>
<div><br>
</div>
<div>Also, remember that by changing the strain you will change the energy position of the bands (as basically all materials have non-zero deformation potentials) and therefore you cannot really compare values at the same exact chemical potential mu.
E.g. it is possible that when you get close to zero, it is because at that strain there’s no band close to the chemical potential (and since you are at low T, you need bands really close). Changing strain, bands enter in the region.</div>
<div><br>
</div>
<div>I suggest that you start by T>50K (and without boltz_tdf_smr_fixed_en_width) and you compare the whole plots in a chemical potential range, and once you understand the behaviour you go down in temperature, potentially putting back some smearing
in the TDF, to check also if you are converged enough. Note however that the TDF smearing while probably needed at low T, might introduce some errors in the final results.</div>
<div><br>
</div>
<div>Hope this helps,</div>
<div><br>
</div>
<div>Giovanni</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
<div>
<div style="color:rgb(0,0,0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
-- <br>
Giovanni Pizzi<br>
Theory and Simulation of Materials and MARVEL, EPFL<br>
<a href="http://people.epfl.ch/giovanni.pizzi" target="_blank">http://people.epfl.ch/<wbr>giovanni.pizzi</a><br>
<a href="http://nccr-marvel.ch/en/people/profile/giovanni-pizzi" target="_blank">http://nccr-marvel.ch/en/<wbr>people/profile/giovanni-pizzi</a></div>
</div>
<br>
<div>
<blockquote type="cite"><div><div class="h5">
<div>On 31 May 2017, at 18:42, Jun Liu <<a href="mailto:jun.physics@gmail.com" target="_blank">jun.physics@gmail.com</a>> wrote:</div>
<br class="m_-4683542062244942626Apple-interchange-newline">
</div></div><div><div><div class="h5">
<div dir="ltr">
<div>
<div>
<div>Dear wannier users,<br>
<br>
</div>
<div>I would like to ask whether the following input for conductivity tensor calculation looks ok.
<br>
<br>
num_bands = 128 ! set to NBANDS by VASP<br>
num_wann = 88<br>
begin projections<br>
Mo:d ! 20<br>
Te:p ! 24<br>
end projections<br>
<br>
###########BoltzWann ############<br>
boltzwann = true<br>
kmesh = 400 400 400<br>
boltz_relax_time = 0.001<br>
boltz_mu_min = 7.95123782 <wbr> #ef-def<br>
boltz_mu_max = 8.35123782<br>
boltz_mu_step = 0.04<br>
boltz_temp_min = 2<br>
boltz_temp_max = 10<br>
boltz_temp_step = 2<br>
boltz_tdf_energy_step=0.01<br>
boltz_tdf_smr_fixed_en_width = 0.01<br>
boltz_tdf_smr_type = gauss<br>
boltz_calc_also_dos = true<br>
boltz_dos_energy_min = 5.0<br>
boltz_dos_energy_max = 15.0<br>
boltz_dos_energy_step = 0.01<br>
##############################<wbr>###<br>
<br>
write_hr = .true.<br>
# Bandstructure<br>
restart = plot<br>
bands_plot = true<br>
begin kpoint_path<br>
....<br>
end kpoint_path<br>
bands_num_points 100 # bands_plot_format gnuplot<br>
<br>
<br>
spinors = .true.<br>
<br>
begin unit_cell_cart<br>
<div> 3.4716802 0.0000000 0.0000000 /*this and the next line changes*/<br>
</div>
<div> 0.0000000 6.3666750 0.0000000 /*accordingly for different cases*/<br>
</div>
0.0000000 0.0000000 13.8452386<br>
end unit_cell_cart<br>
<br>
begin atoms_cart<br>
...<br>
end atoms_cart<br>
<br>
mp_grid = 12 6 3 /*this line differs from each case*/<br>
<br>
begin kpoints<br>
...<br>
end kpoints<br>
<br>
</div>
<div>This input returns reasonable result (in that the conductivity tensor is nearly diagonal for orthorhombic structure). But if I compare results across different cases, they differ too much under as small as 0.5% lattice constant change. More details
are given below.<br>
</div>
<div><br>
</div>
I tried to calculate the conductivity tensor with postw90.x with version 2.1. I tried it on three cases related with slight elongation along a or b directions defining an orthorhombic structure on the original lattice. The resulting conductivity tensor differs
by nearly 100% for a 0.5% lattice constant change, which cannot be right. To give you some numbers, the following shows different sigma_x,x scanned under different chemical potentials for different lattice structures, (other components of sigma are suppressed
for brevity but the whole sigma matrix does show a diagonal feature expected for an orthorhombic structure.)
<br>
<br>
</div>
For the base structure (a,b,c)<br>
</div>
mu T sigma_x,x<br>
<div> 7.963542580 2.000000000 0.4228380355E-05<br>
7.963542580 4.000000000 0.6146815602E-01<br>
7.963542580 6.000000000 1.261398051 <br>
7.963542580 8.000000000 5.250207712 <br>
7.963542580 10.00000000 11.71261179 <br>
<br>
</div>
<div>For the elongated structure along a by 0.5%<br>
mu T sigma_x,x<br>
7.962242580 2.000000000 0.5201871790E-03<br>
7.962242580 4.000000000 0.6688530829 <br>
7.962242580 6.000000000 6.051666588 <br>
7.962242580 8.000000000 16.35207686 <br>
7.962242580 10.00000000 27.52636769 <br>
<br>
</div>
<div>For the elongated structure along b by 0.5%<br>
mu T sigma_x,x<br>
7.951237820 2.000000000 <a href="tel:%28332%29%20903-9665" value="+13329039665" target="_blank">
332.9039665</a> <br>
7.951237820 4.000000000 363.9745377 <br>
7.951237820 6.000000000 287.1196636 <br>
7.951237820 8.000000000 <a href="tel:%28228%29%20918-7157" value="+12289187157" target="_blank">
228.9187157</a> <br>
7.951237820 10.00000000 188.4869745 <br>
<br>
</div>
<div>Any idea on how to check the calculation? Thanks all very much for your insightful help!
<br>
<br>
</div>
<div>Sincerely,<br>
</div>
<div>Jun<br>
</div>
<div><br>
</div>
</div></div></div>
______________________________<wbr>_________________<br>
Wannier mailing list<br>
<a href="mailto:Wannier@quantum-espresso.org" target="_blank">Wannier@quantum-espresso.org</a><br>
<a href="http://mailman.qe-forge.org/cgi-bin/mailman/listinfo/wannier" target="_blank">http://mailman.qe-forge.org/<wbr>cgi-bin/mailman/listinfo/<wbr>wannier</a><br>
</div>
</blockquote>
</div>
<br>
</div>
</div>
<br>______________________________<wbr>_________________<br>
Wannier mailing list<br>
<a href="mailto:Wannier@quantum-espresso.org">Wannier@quantum-espresso.org</a><br>
<a href="http://mailman.qe-forge.org/cgi-bin/mailman/listinfo/wannier" rel="noreferrer" target="_blank">http://mailman.qe-forge.org/<wbr>cgi-bin/mailman/listinfo/<wbr>wannier</a><br>
<br></blockquote></div><br></div>