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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Hello Wannier90 Community,</span><br>
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<div class="x_ContentPasted0">I am trying to compute site symmetric ab initio Tight-Binding models using the site_symmetry=TRUE flag in <seedname>.win. I have followed the online tutorials (2020_03_Oxford/2c_symmetry_adapted) and am able to replicate results
for H3S, GaAs and extend the results to the zincblende phase of SiC using an 8 band sp3 initial projection. However, when I try to modify the system even a little, I get either strange results or error messages.
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<div class="x_ContentPasted0">The example systems I consider here are for a 2 atom unit cell zincblende SiC, a 4 atom unit cell (1x1x2 supecell) zincblende SiC, and a 4 atom unit cell 2H SiC.</div>
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<div class="x_ContentPasted0">Since the 2 atom zincblende converges as expected, I had assumed the 4 atom doubled unit cell would produce similar results and converge, since it is merely zone folded in k-space. This system does converge, but gives Wannier function
centers that are not atom centered. I suspect this has something to do with QE not identifying glide/screw g={t|R} symmetries in systems with pure fractional translation g={t|1} (i.e., supercells). This can be noted in the QE output, where the 2 atom ZB unit
cell has 24 symmetries, whereas the 4 atom ZB unit cell has 6.</div>
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<div class="x_ContentPasted0">The case for 2H (wurtzite) is even worse. I cannot get the system to converge for an sp3 projection, with the error suggesting something wrong with the initial projection. I find this strange since the orbital character of the
states for all three systems specified should be nearly identical.</div>
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<div class="x_ContentPasted0">Attached are the shell scripts that can be run to reproduce the calculations outlined.</div>
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<div>Summary of results</div>
<div>###########################################################</div>
<div class="x_ContentPasted0"> Example for 3C SiC </div>
<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> (Note: this example worked as expected)</div>
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<div class="x_ContentPasted0"> Final State</div>
<div class="x_ContentPasted0"> WF centre and spread 1 ( 0.000000, 0.000000, 0.000000 ) 1.57823570</div>
<div class="x_ContentPasted0"> WF centre and spread 2 ( 0.000000, 0.000000, 0.000000 ) 2.57469067</div>
<div class="x_ContentPasted0"> WF centre and spread 3 ( 0.000000, 0.000000, -0.000001 ) 2.57469307</div>
<div class="x_ContentPasted0"> WF centre and spread 4 ( -0.000000, 0.000002, -0.000000 ) 2.57469073</div>
<div class="x_ContentPasted0"> WF centre and spread 5 ( 1.095076, 1.095076, 1.095076 ) 0.90201541</div>
<div class="x_ContentPasted0"> WF centre and spread 6 ( 1.095076, 1.095076, 1.095076 ) 1.61900198</div>
<div class="x_ContentPasted0"> WF centre and spread 7 ( 1.095076, 1.095076, 1.095076 ) 1.61900244</div>
<div class="x_ContentPasted0"> WF centre and spread 8 ( 1.095076, 1.095076, 1.095076 ) 1.61900196</div>
<div class="x_ContentPasted0"> Sum of centres and spreads ( 4.380305, 4.380306, 4.380303 ) 15.06133196</div>
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<div class="x_ContentPasted0"> where the coordinates match those specified in the projection block and should be the positions of atoms in the unit cell...</div>
<div class="x_ContentPasted0"> (Viewable in many places, but most easily near the top of *.wout)</div>
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<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
<div class="x_ContentPasted0"> | Site Fractional Coordinate Cartesian Coordinate (Ang) |</div>
<div class="x_ContentPasted0"> +----------------------------------------------------------------------------+</div>
<div class="x_ContentPasted0"> | Si 1 -0.00000 -0.00000 -0.00000 | -0.00000 -0.00000 -0.00000 |</div>
<div class="x_ContentPasted0"> | C 1 0.25000 0.25000 0.25000 | 1.09508 1.09508 1.09508 |</div>
<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
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<div class="x_ContentPasted0"> Example for 1x1x2 supercell of 3C-SiC (4 atom unit cell for ZB made by adding R000+R001 unit cells together)</div>
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<div class="x_ContentPasted0"> (Note: This example "ran" and "converged" but the results are non-sense)</div>
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<div class="x_ContentPasted0"> Final State</div>
<div class="x_ContentPasted0"> WF centre and spread 1 ( 0.483907, 0.483907, -0.483907 ) 2.68709962</div>
<div class="x_ContentPasted0"> WF centre and spread 2 ( 0.564237, -0.379955, 0.379955 ) 2.48775520</div>
<div class="x_ContentPasted0"> WF centre and spread 3 ( -0.379955, 0.564237, 0.379955 ) 2.48775525</div>
<div class="x_ContentPasted0"> WF centre and spread 4 ( -0.379955, -0.379955, -0.564238 ) 2.48775592</div>
<div class="x_ContentPasted0"> WF centre and spread 5 ( 0.817993, 0.817993, 1.372159 ) 1.16964635</div>
<div class="x_ContentPasted0"> WF centre and spread 6 ( 1.468481, 1.101956, 1.088195 ) 1.60161090</div>
<div class="x_ContentPasted0"> WF centre and spread 7 ( 1.101956, 1.468481, 1.088195 ) 1.60161060</div>
<div class="x_ContentPasted0"> WF centre and spread 8 ( 1.101956, 1.101956, 0.721671 ) 1.60161275</div>
<div class="x_ContentPasted0"> WF centre and spread 9 ( 2.674063, 2.674064, -0.483912 ) 2.68716225</div>
<div class="x_ContentPasted0"> WF centre and spread 10 ( 2.754390, 1.810196, 0.379955 ) 2.48780836</div>
<div class="x_ContentPasted0"> WF centre and spread 11 ( 1.810196, 2.754390, 0.379956 ) 2.48780761</div>
<div class="x_ContentPasted0"> WF centre and spread 12 ( 1.810196, 1.810196, -0.564238 ) 2.48780878</div>
<div class="x_ContentPasted0"> WF centre and spread 13 ( 3.008153, 3.008152, 1.372150 ) 1.16977422</div>
<div class="x_ContentPasted0"> WF centre and spread 14 ( 3.658659, 3.292089, 1.088214 ) 1.60157323</div>
<div class="x_ContentPasted0"> WF centre and spread 15 ( 3.292089, 3.658659, 1.088214 ) 1.60157287</div>
<div class="x_ContentPasted0"> WF centre and spread 16 ( 3.292090, 3.292089, 0.721644 ) 1.60157170</div>
<div class="x_ContentPasted0"> Sum of centres and spreads ( 27.078454, 27.078454, 7.963969 ) 32.24992563</div>
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<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
<div class="x_ContentPasted0"> | Site Fractional Coordinate Cartesian Coordinate (Ang) |</div>
<div class="x_ContentPasted0"> +----------------------------------------------------------------------------+</div>
<div class="x_ContentPasted0"> | Si 1 0.00000 0.00000 0.00000 | 0.00000 0.00000 0.00000 |</div>
<div class="x_ContentPasted0"> | Si 2 0.00000 0.00000 0.50000 | 2.19015 2.19015 0.00000 |</div>
<div class="x_ContentPasted0"> | C 1 0.25000 0.25000 0.12500 | 1.09508 1.09508 1.09508 |</div>
<div class="x_ContentPasted0"> | C 2 0.25000 0.25000 0.62500 | 3.28523 3.28523 1.09508 |</div>
<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> Example for 2H-SiC (4 atom primitve wurtzite unit cell for SiC)</div>
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<div class="x_ContentPasted0"> (Note: this example did not run... specifically the final step with wannier90.x gives a convergence error and terminates)</div>
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<div class="x_ContentPasted0"> Error in symmetrize_u: not converged</div>
<div class="x_ContentPasted0"> Either eps is too small or specified irreps is not</div>
<div class="x_ContentPasted0"> compatible with the bands</div>
<div class="x_ContentPasted0"> diff,eps= 0.2910700672E+02 0.1000000000E-06</div>
<div class="x_ContentPasted0"> Exiting.......</div>
<div class="x_ContentPasted0"> symmetrize_ukirr: not converged</div>
<div class="x_ContentPasted0"> </div>
<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
<div class="x_ContentPasted0"> | Site Fractional Coordinate Cartesian Coordinate (Ang) |</div>
<div class="x_ContentPasted0"> +----------------------------------------------------------------------------+</div>
<div class="x_ContentPasted0"> | Si 1 0.00000 0.00000 0.00000 | 0.00000 0.00000 0.00000 |</div>
<div class="x_ContentPasted0"> | Si 2 0.33333 -0.33333 0.50000 | 0.00000 1.78692 2.53571 |</div>
<div class="x_ContentPasted0"> | C 1 0.00000 0.00000 0.37677 | 0.00000 0.00000 1.91076 |</div>
<div class="x_ContentPasted0"> | C 2 0.33333 -0.33333 0.87677 | 0.00000 1.78692 4.44647 |</div>
<div class="x_ContentPasted0"> *----------------------------------------------------------------------------*</div>
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<div class="x_ContentPasted0">I am looking for advice on how/why I am getting error messages and how to get quality converged results when using site_symmetry=TRUE in wannier90 (combined with quantum espresso (QE) and pw2wannier90's flag write_dmn=True).</div>
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Thanks!<br>
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Joseph Sink, PhD</div>
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Postdoctoral Fellow</div>
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University of Iowa, Iowa City, Iowa</div>
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Department of Physics and Astronomy</div>
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