Hello,
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.
kind regards
On 25/08/2025 20:31, Barsha Pal wrote:
Hello everyone,
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
( energy convergence thresh.= 1.0E-05
force convergence thresh. = 1.0E-04
press convergence thresh. = 5.0E-03)
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.
The input specifications are:
&CONTROL
calculation = "vc-relax"
restart_mode = "from_scratch"
outdir = "/tmp/"
prefix = "pwscf"
pseudo_dir = "/p/"
verbosity = "high"
etot_conv_thr = 1.0D-6
forc_conv_thr = 1.0D-5
nstep = 1000
tprnfor = .true.
disk_io = "none"
/
&SYSTEM
ibrav = 0
celldm(1) = 14.629678225
nat = 8
ntyp = 2
ecutwfc = 170
ecutrho = 680
occupations = "smearing"
smearing = "mv"
degauss = 0.005
/
&ELECTRONS
electron_maxstep = 600
mixing_beta = 0.3
conv_thr = 1.0d-6
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
press = 0.0
cell_dynamics = "bfgs"
cell_dofree = "2Dxy"
/
ATOMIC_SPECIES
A 000 A.pbe-dnl-kjpaw_psl.1.0.0.UPF
B 00 B.pbe-nl-kjpaw_psl.1.0.0.UPF
CELL_PARAMETERS (alat= 14.629678225 )
1.000000000 0.000000000 0.000000000
0.000000000 1.000000000 0.000000000
0.000000000 0.000000000 2.583596722
ATOMIC_POSITIONS (crystal)
A 0.6470402285 0.1471007113 0.5000000000
B 0.6491194122 0.8509186097 0.5000000000
B 0.3508805878 0.1490813903 0.5000000000
A 0.3529597715 0.8528992887 0.5000000000
A 0.1471007113 0.3529597715 0.5000000000
B 0.8509186097 0.3508805878 0.5000000000
B 0.1490813903 0.6491194122 0.5000000000
A 0.8528992887 0.6470402285 0.5000000000
K_POINTS {automatic}
12 12 3 0 0 0
NOTE: This is supposed to be a 2D surface with buckling and with a
band gap.
Ashley Cooper
Phd
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Dr. Lorenzo Paulatto
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN
phone: +33 (0)1 442 79822 / telegram: lpaulatto
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
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_______________________________________________________________________________
The Quantum ESPRESSO Foundation stands in solidarity with all civilians
worldwide who are victims of terrorism, military aggression, and indiscriminate
warfare.
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