Hello Wannier90 Community, 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.
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. 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. 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. Attached are the shell scripts that can be run to reproduce the calculations outlined. Summary of results ########################################################### Example for 3C SiC (Note: this example worked as expected) Final State WF centre and spread 1 ( 0.000000, 0.000000, 0.000000 ) 1.57823570 WF centre and spread 2 ( 0.000000, 0.000000, 0.000000 ) 2.57469067 WF centre and spread 3 ( 0.000000, 0.000000, -0.000001 ) 2.57469307 WF centre and spread 4 ( -0.000000, 0.000002, -0.000000 ) 2.57469073 WF centre and spread 5 ( 1.095076, 1.095076, 1.095076 ) 0.90201541 WF centre and spread 6 ( 1.095076, 1.095076, 1.095076 ) 1.61900198 WF centre and spread 7 ( 1.095076, 1.095076, 1.095076 ) 1.61900244 WF centre and spread 8 ( 1.095076, 1.095076, 1.095076 ) 1.61900196 Sum of centres and spreads ( 4.380305, 4.380306, 4.380303 ) 15.06133196 where the coordinates match those specified in the projection block and should be the positions of atoms in the unit cell... (Viewable in many places, but most easily near the top of *.wout) *----------------------------------------------------------------------------* | Site Fractional Coordinate Cartesian Coordinate (Ang) | +----------------------------------------------------------------------------+ | Si 1 -0.00000 -0.00000 -0.00000 | -0.00000 -0.00000 -0.00000 | | C 1 0.25000 0.25000 0.25000 | 1.09508 1.09508 1.09508 | *----------------------------------------------------------------------------* Example for 1x1x2 supercell of 3C-SiC (4 atom unit cell for ZB made by adding R000+R001 unit cells together) (Note: This example "ran" and "converged" but the results are non-sense) Final State WF centre and spread 1 ( 0.483907, 0.483907, -0.483907 ) 2.68709962 WF centre and spread 2 ( 0.564237, -0.379955, 0.379955 ) 2.48775520 WF centre and spread 3 ( -0.379955, 0.564237, 0.379955 ) 2.48775525 WF centre and spread 4 ( -0.379955, -0.379955, -0.564238 ) 2.48775592 WF centre and spread 5 ( 0.817993, 0.817993, 1.372159 ) 1.16964635 WF centre and spread 6 ( 1.468481, 1.101956, 1.088195 ) 1.60161090 WF centre and spread 7 ( 1.101956, 1.468481, 1.088195 ) 1.60161060 WF centre and spread 8 ( 1.101956, 1.101956, 0.721671 ) 1.60161275 WF centre and spread 9 ( 2.674063, 2.674064, -0.483912 ) 2.68716225 WF centre and spread 10 ( 2.754390, 1.810196, 0.379955 ) 2.48780836 WF centre and spread 11 ( 1.810196, 2.754390, 0.379956 ) 2.48780761 WF centre and spread 12 ( 1.810196, 1.810196, -0.564238 ) 2.48780878 WF centre and spread 13 ( 3.008153, 3.008152, 1.372150 ) 1.16977422 WF centre and spread 14 ( 3.658659, 3.292089, 1.088214 ) 1.60157323 WF centre and spread 15 ( 3.292089, 3.658659, 1.088214 ) 1.60157287 WF centre and spread 16 ( 3.292090, 3.292089, 0.721644 ) 1.60157170 Sum of centres and spreads ( 27.078454, 27.078454, 7.963969 ) 32.24992563 *----------------------------------------------------------------------------* | Site Fractional Coordinate Cartesian Coordinate (Ang) | +----------------------------------------------------------------------------+ | Si 1 0.00000 0.00000 0.00000 | 0.00000 0.00000 0.00000 | | Si 2 0.00000 0.00000 0.50000 | 2.19015 2.19015 0.00000 | | C 1 0.25000 0.25000 0.12500 | 1.09508 1.09508 1.09508 | | C 2 0.25000 0.25000 0.62500 | 3.28523 3.28523 1.09508 | *----------------------------------------------------------------------------* Example for 2H-SiC (4 atom primitve wurtzite unit cell for SiC) (Note: this example did not run... specifically the final step with wannier90.x gives a convergence error and terminates) Error in symmetrize_u: not converged Either eps is too small or specified irreps is not compatible with the bands diff,eps= 0.2910700672E+02 0.1000000000E-06 Exiting....... symmetrize_ukirr: not converged *----------------------------------------------------------------------------* | Site Fractional Coordinate Cartesian Coordinate (Ang) | +----------------------------------------------------------------------------+ | Si 1 0.00000 0.00000 0.00000 | 0.00000 0.00000 0.00000 | | Si 2 0.33333 -0.33333 0.50000 | 0.00000 1.78692 2.53571 | | C 1 0.00000 0.00000 0.37677 | 0.00000 0.00000 1.91076 | | C 2 0.33333 -0.33333 0.87677 | 0.00000 1.78692 4.44647 | *----------------------------------------------------------------------------* 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). Thanks! Joseph Sink, PhD Postdoctoral Fellow University of Iowa, Iowa City, Iowa Department of Physics and Astronomy
2H_SiC_run.shell
Description: 2H_SiC_run.shell
3C_doubled_SiC_run.sh
Description: 3C_doubled_SiC_run.sh
3C_SiC_run.shell
Description: 3C_SiC_run.shell
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