Hello, everyone
I need some help regarding elastic constant calculation of LiMgF3 compound. I am facing following issue:
task # 0
from initialize_elastic_cons : error # 1
Laue class not available
task # 1
from initialize_elastic_cons : error # 1
Laue class not available
My pw.x input file is as follows:
&CONTROL
calculation = "relax"
forc_conv_thr = 1.00000e-03
max_seconds = 1.72800e+05
nstep = 100
pseudo_dir = "./"
/
&SYSTEM
a = 3.958
degauss = 1.00000e-02
ecutrho = 5.23088e+02
ecutwfc = 5.81209e+01
input_DFT = "PBE"
ibrav = 1
nat = 5
ntyp = 3
occupations = "smearing"
smearing = "gaussian"
/
&ELECTRONS
conv_thr = 1.00000e-06
electron_maxstep = 200
mixing_beta = 7.00000e-01
startingpot = "atomic"
startingwfc = "atomic+random"
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
/
K_POINTS {automatic}
3 3 3 0 0 0
ATOMIC_SPECIES
Li 6.9400 Li.pbe-mt_fhi.UPF
Mg 24.305 Mg.pbe-mt_fhi.UPF
F 18.998 F.pbe-mt_fhi.UPF
ATOMIC_POSITIONS {angstrom}
Li 0.000000 0.000000 0.000000
Mg 1.904000 1.904000 1.904000
F 1.904000 0.000000 1.904000
F 1.904000 1.904000 0.000000
F 0.000000 1.904000 1.904000
And thermo_control file is as follows:
&INPUT_THERMO
what='elastic_constants_t',
frozen_ions=.FALSE.
elastic_algorithm='energy'
use_free_energy=.TRUE.
lmurn=.FALSE.
tmin=1.,
tmax=3000.,
deltat=3.,
/
Please help me in this regards. Thanks
Hello Muhammad Mubashir
Thermo_pw, as well as Quantum ESPRESSO, has a particular way to deal with structure symmetry. When we begin to use them, we think that it was just set ibrav=1, and they would compute the right symmetry. It's not like this. The most important part of set a symmetry in Quantum ESPRESSO are the atomic positions.
Do a simple SCF calculation, and check how many symmetries were detected in your system. Look for this section in output file:
atomic species valence mass pseudopotential
Cs 9.00 132.90545 Cs( 1.00)
Pb 14.00 207.21000 Pb( 1.00)
I 7.00 126.90447 I ( 1.00)
48 Sym. Ops., with inversion, found
The point is PW and Thermo_pw can detect the symmetry of the systems we determine in input file. I think there might have a problem with your system's symmetry. And I think you should relax your cell before using thermo_pw, preserving symmetry with te command dofree=ibrav.
Let me know if you need more help with this.
Best regards,
Ricardo Tadeu.
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