[Pw_forum] About phonon calculation and IR

[Diep Vinh Quang]

Dear all,

Thank you very much for your reply and your help.

I would like to ask some question about phonon calculation at gamma:

1. Why the propram phcg.x cannot use with  ultra-solf pseudopotentials ?
what is the different between phcp.x and ph.x

2. When i calculated the phonon at gamma by using ph.x, the effective
charge in the dynamical matrix does not satisfy the ASR (the geometry of
Polyethylene is this case for sure is correct). I don't know the reason. I
thought that dues to the number of K sampling is a few in my input file:

______________________
 &control
    calculation='scf',
    restart_mode='from_scratch',
    prefix='pe',
    pseudo_dir = '/afs/ictp.trieste.it/home/v/vdiep/espresso-2.1.3/pseudo/'
    outdir='/tmp/'
 /
 &system
      ibrav=8,
      celldm(1) = 13.479600
      celldm(2) = 0.717398
      celldm(3) = 0.360998
      nat=12 , ntyp= 2,
      ecutwfc =40.0,
 /
 &electrons

    mixing_beta = 0.7
    conv_thr =  1.0d-8
 /
ATOMIC_SPECIES
 C  12.0107  C.pbe-van_bm.UPF
 H  1.00794  H.pbe-van_bm.UPF

ATOMIC_POSITIONS {angstrom}
C       -0.245695461  -0.316717589   0.644009287
H        0.039558649  -1.384963029   0.644168352
H       -1.351501461  -0.307736442   0.644163171
C        0.245572450   0.316642176  -0.644005418
H       -0.039700505   1.384882483  -0.644164826
H        1.351378971   0.307677348  -0.644159390
C        3.320929864   2.875316272   1.931505401
H        2.215124940   2.866341694   1.931659329
H        3.606194345   3.943558228   1.931664829
C        3.812198945   2.241955578   0.643490878
H        4.918003969   2.250929351   0.643336802
H        3.526935295   1.173713930   0.643331585


K_POINTS {automatic}
2 2 2 0 0 0
_____________________

and phonon input file


 &inputph
  tr2_ph=1.0d-14,
  prefix='pe',
  epsil=.true.
  amass(1)=12.0107,
  amass(2)=1.00794,
  outdir='/tmp/'
  fildyn='pe.dynG',
 /
0.0 0.0 0.0
-------------------------------


But when i try to increase the number of k points (4 4 4 0 0 0) in scf
inplut, the ph.x doesnot recognize this change, It's still using 8 k's
points as in the case (2 2 2 0 0 0). How can we solve this problem.

Thank you very much.

Vinh



-------------------------------------------------
Diep Vinh Quang
C/o Diploma Program, The Abdus Salam
International Center for Theoretical Physics(ICTP),
11 Strada Costiera, 34014, Trieste,Italy.
http://www.ictp.it