ABINIT Discussion Forums

Posted: **Wed May 01, 2013 7:18 pm**

Dear all,
The output of Raman already has phonon frequencies and energies.
So, is it possible to draw phonon structure using non-linear response calculation (Raman calculation) output file's information?

regards,
jek

Posted: **Thu May 02, 2013 3:27 am**

What do you mean, "draw the phonon structure"? If you just want the phonon frequencies at Gamma, you don't have to do all the work of a Raman calculation, just do a phonon calc at the gamma point itself.

Posted: **Sun May 05, 2013 10:59 am**

jzwanzig wrote:What do you mean, "draw the phonon structure"? If you just want the phonon frequencies at Gamma, you don't have to do all the work of a Raman calculation, just do a phonon calc at the gamma point itself.

Hello Professor Zwanziger, thanks for your replay.
I want to get phonon dispersion curves wit (Г-M-K-Г) for graphene mono and bilayers.

I am new user of Abinit and I don't know following things:
1.How can i chose the sets of qpt2, qpt3, ...qpt10 etc
2. What is the rule to chose nph1l and qph1l of anaddb
3. How can i plot phonon dispersion curves (Г-M-K-Г)

Could you give me advise

thank you
jek

Code: Select all

# Crystalline graphene bilayer: computation of the phonon spectrum

   ndtset   10
#Set 1 : ground state self-consistency

  getwfk1   0
  kptopt1   1
    nqpt1   0
  tolvrs1   1.0d-18
  rfphon1   0 
 
#Q vectors for all datasets
    nqpt   1 

     qpt2    #???
     qpt3    #???
     qpt4    #???
     qpt5    #???
     qpt6    #???
     qpt7    #???
     qpt8    #???
     qpt9    #???
     qpt10   #???


#Set 2 : Response function calculation of d/dk wave function 

    iscf2   -3         # Need this non-self-consistent option for d/dk
  kptopt2   2          # Modify default to use time-reversal symmetry
  rfphon2   0          # Cancel default
  rfelfd2   2          # Calculate d/dk wave function only
  tolwfr2   1.0d-22    # Use wave function residual criterion instead

#Set 3 : Response function calculation of Q=0 phonons and electric field pert.

  getddk3   2          # d/dk wave functions from last dataset
  kptopt3   2          # Modify default to use time-reversal symmetry
  rfelfd3   3          # Electric-field perturbation response only

#Sets 4-10 : Finite-wave-vector phonon calculations (defaults for all datasets)

   getwfk   1          # Use GS wave functions from dataset1
   kptopt   3          # Need full k-point set for finite-Q response
   rfphon   1          # Do phonon response
  rfatpol   1 4        # Treat displacements of all atoms
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-8 
   
#######################################################################
#Common input variables 

acell   2.46  2.46  30 angstrom
angdeg  90  90  120
ntypat  1
znucl  6
natom 4
typat 1 1 1 1
xred  0.0  0.0  0.0   # 1st layer
      1/3  2/3  0.0
      0.0  0.0  1/2   # 2nt layer
     2/3  1/3  1/2

#Plane wave basis and k-point grid
#*********************************
ecut 40
ngkpt    13 13 1   # 9 9 1
nshiftk  1
shiftk   0 0 0 0   # 0 0 0.5
nband    8

ixc  7
iscf  7
nstep  1000

Anaddb (2. What is the rule to chose nph1l and qph1l of anaddb)

Code: Select all

!Input file for the anaddb code.                     

!Flags
 ifcflag   1     ! Interatomic force constant flag

!Wavevector grid number 1 (coarse grid, from DDB)
  brav    4      ! Bravais Lattice : 1-S.C., 2-F.C., 3-B.C., 4-Hex.)
  ngqpt   13 13 1   ! Monkhorst-Pack indices
  nqshft  1         ! number of q-points in repeated basic q-cell
  q1shft  0 0 0

!Effective charges
     asr   1     ! Acoustic Sum Rule. 1 => imposed asymetrically
  chneut   1     ! Charge neutrality requirement for effective charges.

!Interatomic force constant info
  dipdip  1      ! Dipole-dipole interaction treatment

!Phonon band structure output for band2eps - See note near end for
! dealing with gamma LO-TO splitting issue.
   eivec  4

!Wavevector list number 1 (Reduced coordinates and normalization factor)         
  nph1l    ??                                           ! number of phonons in list 1                             
  qph1l   0.00  0.00  0.00   1.0    !(gamma point)
            ????   ???    ???     1.0      !(M point)
            ???   ????   ???    1.0      !(K point)
            1.00  1.00  1.00   1.0     !(gamma point)
!Wavevector list number 2 (Cartesian directions for non-analytic gamma phonons)
  nph2l    1
  qph2l   1.0  0.0  0.0    0.0

Posted: **Sun May 05, 2013 12:38 pm**

Your first question is answered in section 1 of the 2nd tutorial on response functions, it describes the process of poperly choosing the qpts to use. This tutorial goes on to describe the anaddb input. As to where the interesting points in q space are for your structure, I have no idea because that's very dependent on the structure itself, however, you might look at the Bilbao Crystallographic Server, which will give you plots of the the BZ's of different space groups and the coordinates of the special symmetry positions. Finally, for plotting, the anaddb output will be an ascii file of frequencies for each qpt you choose to interpolote to so you can use whatever plotting software you like.

Posted: **Sun May 05, 2013 12:58 pm**

Thank you for your advise.

Bilbao Crystallographic Server is helpful for me

thank you again

ABINIT Discussion Forums

phonon structure

phonon structure

Re: phonon structure

Re: phonon structure

Re: phonon structure

Re: phonon structure