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Dear Philip </div>
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<br>
</div>
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Final orbitals corresponding to degenerate set of levels may always be different sets of wavefunctions spanning the same manifold. </div>
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This may happen for a lot of reasons (e.g. a different number of MPI ranks, using a different diagonalization algorithm). </div>
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<br>
</div>
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In your case the reason may be that you are running using a different set of symmetries in the 2 cases. </div>
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<br>
</div>
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In supercell calculations, all symmetries that include a fractional translation are disabled. </div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">This makes the program exclude more symmetries in the second setup ( the 3 symmetry equivalent k points in the second run are points that are symmetry equivalent
only using operations that have been excluded). </span><br>
</div>
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<br>
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To avoid symmetrisation, and possibly (not warranted though) end up with the same orbitals you may use the &system flags:</div>
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nosym = .true. </div>
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</div>
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or the safer </div>
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nosym_evc = .true. </div>
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</div>
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I hope it works, but it's not guaranteed that you will obtain the same set of orbitals even without symmetries. </div>
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<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">best regards </span></div>
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Pietro </div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>Da:</b> users <users-bounces@lists.quantum-espresso.org> per conto di Phillip Thomas <PThomas@lbl.gov><br>
<b>Inviato:</b> marted́ 2 agosto 2022 03:03<br>
<b>A:</b> users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
<b>Oggetto:</b> [QE-users] Translated orbitals in periodic calculation</font>
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<div>Dear QE team,</div>
<div><br>
</div>
<div>I have an issue regarding orbitals generated from QE 7.0 runs on two different translated variants of a Silicon lattice. I am using a primitive cubic cell containing 8 atoms instead of the simplest 2-atom unit cell (as I need to pass the output orbitals
to another program which only accepts a tetragonal cell geometry).</div>
<div><br>
</div>
<div>Here is the input file for 'pw.x' for the first variant:</div>
<div>--------------------------------</div>
<div>&control<br>
prefix = 'silicon'<br>
calculation = 'scf'<br>
tstress = .true.<br>
etot_conv_thr = 1d-5<br>
forc_conv_thr = 1d-4<br>
/<br>
&system<br>
ibrav = 1<br>
celldm(1) = 10.173697855629921<br>
nat = 8<br>
ntyp = 1<br>
nbnd = 32<br>
ecutwfc = 80.0<br>
/<br>
&electrons<br>
electron_maxstep = 100<br>
conv_thr = 1.0d-8<br>
mixing_mode = 'plain'<br>
mixing_beta = 0.7<br>
mixing_ndim = 8<br>
diagonalization = 'david'<br>
diago_david_ndim = 4<br>
diago_full_acc = .true.<br>
/<br>
&ions<br>
/<br>
ATOMIC_SPECIES<br>
Si 28.086 Si.pw-mt_fhi.UPF<br>
ATOMIC_POSITIONS alat<br>
Si 0.00 0.00 0.00<br>
Si 0.00 0.50 0.50<br>
Si 0.50 0.00 0.50<br>
Si 0.50 0.50 0.00<br>
Si 0.25 0.25 0.25<br>
Si 0.75 0.75 0.25<br>
Si 0.25 0.75 0.75<br>
Si 0.75 0.25 0.75<br>
K_POINTS automatic<br>
4 4 4 0 0 0</div>
<div>--------------------------------</div>
<div>The second variant has the same input file except that the coordinates of the atoms are shifted to:</div>
<div><br>
</div>
<div> Si 0.125 0.125 0.125<br>
Si 0.125 0.625 0.625<br>
Si 0.625 0.125 0.625<br>
Si 0.625 0.625 0.125<br>
Si 0.375 0.375 0.375<br>
Si 0.875 0.875 0.375<br>
Si 0.375 0.875 0.875<br>
Si 0.875 0.375 0.875<br>
</div>
<div><br>
</div>
<div>Both calculations give the same total energy, -63.52598191 Ry, as I would expect, and the same band structure (except that three additional symmetry equivalent bands are printed out in the latter case); the bands for matching KPOINTS are also the same
in both runs, all as expected. Here are the bands for the 0 0 0 KPOINT for reference:<br>
</div>
<div>--------------------------------</div>
<div> End of self-consistent calculation<br>
<br>
k = 0.0000 0.0000 0.0000 ( 12797 PWs) bands (ev):<br>
<br>
-5.8606 -1.6207 -1.6207 -1.6207 -1.6207 -1.6207 -1.6207 3.3705<br>
3.3706 3.3706 3.3706 3.3706 3.3706 6.2827 6.2827 6.2827<br>
6.8712 6.8712 6.8712 6.8712 6.8712 6.8712 8.8517 8.8517<br>
8.8517 9.6765 14.0241 14.0783 14.0783 16.4618 16.4618 16.4618<br>
</div>
<div>--------------------------------</div>
<div>Now I would like to generate the orbitals for the 0 0 0 KPOINT in cube file format, so here is my input to ''pp.x':</div>
<div>--------------------------------</div>
<div> &inputpp<br>
prefix='silicon'<br>
plot_num=7<br>
kband(1)=1<br>
kband(2)= 32<br>
kpoint=1<br>
lsign=.true.<br>
/<br>
&plot<br>
iflag=3<br>
output_format=6<br>
/</div>
<div>--------------------------------</div>
<div><br>
</div>
<div>When I visually inspect the orbitals, I find that many of the orbitals are qualitatively different for the two translated variants of the lattice; they are not simply translated variants of the same orbital as I would expect. I have attached plots of the
highest occupied orbital (#16) as examples.</div>
<div><br>
</div>
<div>So I am curious, is there a mistake in my inputs or procedure that would cause differences like these? If not, then is there a way in QE that I can generate the orbitals such that they are translationally invariant? Many thanks for looking into this!</div>
<div><br>
</div>
<div>Kind regards,</div>
<div><br>
</div>
<div>Phillip Thomas, Ph.D.<br>
</div>
<div>National Energy Research Scientific Computing Center<br>
</div>
<div>Lawrence Berkeley National Laboratory<br>
</div>
</div>
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