[Phonopy-users] Using Phonopy

[Ashish B. <ash...@gm...>]

Hi all,
I need your kind help in calculating Phonon DOS for my system

I have relaxed my structure using the following tags in vasp

NCORE = 8
 Startparameter for this Run:
  NWRITE =  1       (LPETIM=F    write-flag & time)
  ISTART =  0     !0=new, 1=wave, 2=same cutoff&latt (1&2 need WAVECAR
#  ICHARG =  0    !0=charge from wave, 1=charge from CHGCAR, 2=atom
#  ISPIN = 2
  LWAVE = .FALSE.   (TRUE-Write WAVECAR, FALSE-not)
  LCHARG = .FALSE.  (TRUE-Write CHGCAR and CHG, FALSE-not)
  GGA = PE

Electronic Relaxation
   ENCUT = 525.0
   PREC =  Accurate        !Medium=default, Low, High; affects ENMAX, mesh,
pspot
   EDIFF  =  1E-8    !energy stopping-criterion for electr. iterations
   EDIFFG =  -0.0001     !force stopping-criterion for geometry steps

 Ionic Relaxation
   NSW    = 500    !max number of geometry steps
   NELM   = 200
   NELMDL = -12
   IBRION =  1     !ionic relax: 0-MD 1-quasi-New (RMM-DIIS for NEB)
   ISIF   =  2   !(0:force=y stress=n ions=y shape=n volume=n,
#  1:f=y s=diag i=y s=n v=n, 4:f=y s=y i=y s=y v=n, 5:f=y s=y i=n s=y v=n)
   ISYM   =  1     !1=use symmetry, 0 = no symmetry
   #POTIM  = .25  !initial time step for geo-opt (increase for soft sys)

 DOS related values:
   ISMEAR =      1     ! -4-tet -1-fermi 1=Methfessel/Paxton 1.order
   SIGMA  =     .05     !broadening in eV
 Electronic Relaxation
   ALGO = Normal
#   IALGO  = 48    !algorithm (8=CG for small, 48=RMM for big systems)
   LREAL  = FALSE         !real-space projection

After that I move CONTCAR to POSCAR and  want to use phonopy So I simply
change IBRION=1 to IBRION=8. in my INCAR.

 Now at some places I found NSW=1 with IBRION=8 for calculating Phonon DOS
using Phonopy. So should I set NSW=500 or should I use NSW=1?

Also please tell me whether EDIFF=1E-8 and EDIFFG=-0.0001 is sufficient
condition for phonopy if not then how should i check the optimum condition?

Thanks
-- 
Ashish Bhatnagar
Senior Research Fellow
Hydrogen Energy Centre, Dept. of Physics
Banaras Hindu University, Varanasi
India - 221005