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<p>Hello,</p>
<p>if the initial position have high symmetry, the relaxation will
not be able to break the symmetry. You need to break the symmetry
by hand, by moving the atoms a bit, before relaxing in order to
achieve a buckled structure.</p>
<p>kind regards<br>
</p>
<div class="moz-cite-prefix">On 25/08/2025 20:31, Barsha Pal wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAE7kQ+z9PDV44sQC4J49Q7robAz5E_BMeuWgCcgi-LDGSaHHcg@mail.gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div dir="ltr">Hello everyone,
<div>I am trying to optimize a structure existing in literature.
It is reported to have buckling not planar. I made the
pristine (only carbon -- totally planar) analogue of the
structure and doped it to my target. Now on optimizing the z
coordinates do not change at all. I need the z to be changed
as well to get the target buckling. Also the optimization
converged for a loose criteria </div>
<div>( energy convergence thresh.= 1.0E-05</div>
force convergence thresh. = 1.0E-04<br>
<div> press convergence thresh. = 5.0E-03) </div>
<div>and when I tighten the criteria, BFGS fails. I have tried
optimizing with and without cell_dofree = all and 2Dxy, but
the z remains unchanged.</div>
<div><br>
</div>
<div><br>
</div>
<div>The input specifications are:</div>
<div><br>
</div>
<div>&CONTROL<br>
calculation = "vc-relax"<br>
restart_mode = "from_scratch"<br>
outdir = "/tmp/"<br>
prefix = "pwscf"<br>
pseudo_dir = "/p/"<br>
verbosity = "high"<br>
etot_conv_thr = 1.0D-6<br>
forc_conv_thr = 1.0D-5<br>
nstep = 1000<br>
tprnfor = .true.<br>
disk_io = "none"<br>
/<br>
<br>
&SYSTEM<br>
ibrav = 0<br>
celldm(1) = 14.629678225<br>
nat = 8<br>
ntyp = 2<br>
ecutwfc = 170<br>
ecutrho = 680<br>
occupations = "smearing"<br>
smearing = "mv"<br>
degauss = 0.005<br>
<br>
/<br>
<br>
&ELECTRONS<br>
electron_maxstep = 600<br>
mixing_beta = 0.3<br>
conv_thr = 1.0d-6<br>
/<br>
<br>
&IONS<br>
ion_dynamics = "bfgs"<br>
/<br>
<br>
&CELL<br>
press = 0.0<br>
cell_dynamics = "bfgs"<br>
cell_dofree = "2Dxy"<br>
/<br>
<br>
ATOMIC_SPECIES<br>
A 000 A.pbe-dnl-kjpaw_psl.1.0.0.UPF<br>
B 00 B.pbe-nl-kjpaw_psl.1.0.0.UPF<br>
<br>
CELL_PARAMETERS (alat= 14.629678225 )<br>
1.000000000 0.000000000 0.000000000<br>
0.000000000 1.000000000 0.000000000<br>
0.000000000 0.000000000 2.583596722<br>
<br>
ATOMIC_POSITIONS (crystal)<br>
A 0.6470402285 0.1471007113
0.5000000000<br>
B 0.6491194122 0.8509186097
0.5000000000<br>
B 0.3508805878 0.1490813903
0.5000000000<br>
A 0.3529597715 0.8528992887
0.5000000000<br>
A 0.1471007113 0.3529597715
0.5000000000<br>
B 0.8509186097 0.3508805878
0.5000000000<br>
B 0.1490813903 0.6491194122
0.5000000000<br>
A 0.8528992887 0.6470402285
0.5000000000<br>
<br>
K_POINTS {automatic}<br>
12 12 3 0 0 0</div>
<div><br>
</div>
<div><br>
</div>
<div>NOTE: This is supposed to be a 2D surface with buckling and
with a band gap.</div>
<div><br>
</div>
<div><br>
</div>
<div>Ashley Cooper</div>
<div>Phd</div>
</div>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
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</blockquote>
<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN <br>
phone: +33 (0)1 442 79822 / telegram: lpaulatto<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
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