[Pw_forum] PHonon underestimates the dielectric tensor

[Mohamed Elshazly]

Hello everyone,


I'm trying to reproduce the dielectric constant of alpha-alumina using PHonon. However, I'm getting values close to third of the actual dielectric constant and cannot figure out why. I also had the same issue with Columbite-(Mg), so it's not a particular problem with that material system.


Here are my SCF and PH input files:


&control
calculation='scf',
outdir='./out',
prefix='alo',
pseudo_dir='.',
tstress=.true.,
tprnfor=.true.,
forc_conv_thr=1.0D-8,
etot_conv_thr=1.0D-6,
/

&system
ibrav=0,
celldm(1)=9.69051561,
nat=10,
ntyp=2,
ecutwfc=50,
/

&electrons
diago_full_acc=.true.,
/

&ions
/

ATOMIC_SPECIES
O 15.9994 O.pbe-mt.UPF
Al 26.981539 Al.pbe-mt_fhi

CELL_PARAMETERS alat
   0.444822702  -0.256818507   0.805845773
  -0.000000000   0.513637014   0.805845773
  -0.444822702  -0.256818507   0.805845773

ATOMIC_POSITIONS crystal
O        0.058814216   0.749985721   0.441239527
O        0.250014279   0.558760473   0.941185784
O        0.441239527   0.058814216   0.749985721
O        0.558760473   0.941185784   0.250014279
O        0.749985721   0.441239527   0.058814216
O        0.941185784   0.250014279   0.558760473
Al       0.148217545   0.148217545   0.148217545
Al       0.351772827   0.351772827   0.351772827
Al       0.648227173   0.648227173   0.648227173
Al       0.851782455   0.851782455   0.851782455

K_POINTS automatic
16 16 16 0 0 0

PH:

alo_dielectric

&INPUTPH
tr2_ph=1e-15,
outdir='./out',
prefix='alo',
epsil=.true.,
/

0 0 0

Any help would be greatly appreciated.

Mohamed Elshazly
Edward S. Rogers Department of Electrical and Computer Engineering
University of Toronto




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