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["Corsin Battaglia" <corsin.battaglia@freesurf.ch>]

Dear abinit users

 

Well, I do not really have obtained a bandstructure for the phonons yet.

But I am trying to calculate the phonon dispersion of the metallic compound 1T-NbTe2. Since it is metallic, I am just using the phonon type perturbation and neglecting the electric field type perturbation.

My input file is based on test t26.in (phonon bandstructure of Al) and the infos given in the respfn-help file.

There are several problems:

 

1) I get 6 accoustic phonon modes at q=0.

 

2) The RF-SCF cycles do not converge (tolvrs* 1.0d-10) (dataset 5).

 

3) I can not get rid of the feeling that I am calculating to many q-points and that their might be a much more economic way to get the bandstructure exploiting the DDB with the help of ifc=anaddb. In the header of the t26.in file it says that 6 dynamical matrices are needed for the computation of the full phonon bandstructure of Al. There are as well six different q-vector for which an RF calculation is performed.

Does this also mean that I will get 6 DDB's which I have to merge and from which I can compute the eigenfrequencies using anaddb?

How to decide which q-vectors must be included in the DDB?

Horacio W. Leite Alves, in response to Kwan-Woo Lee's mail, mentions that only the gamma-point DDB is needed. Does this also apply to my case? Then why do we need the DDB merge tool?

Are the eigenenergies I get from abinit the same as the one from anaddb (without imposing the accoustic sum rule)?

 

My input file is attached. Thanks in advance for your help.

 

Corsin

 

P.S.: The electronic bandstructure is great now!!!

 

 

My input file:

********************************************************************

 

 

# NbTe2 phonon band structure

 

 ndtset 13

 

 nbdbuf 2

 

#Input that is common to most datasets, but not all
  getden 1
  getwfk 2
  kptopt 3
  nqpt 1

 

#Dataset 1 : SCF

 

  getden1  0
  getwfk1  0
  kptopt1  1
    nqpt1  0
  prtden1  1
    iscf1  5
  tolvrs1  1.0d-13
 
#Dataset 2 : non-SCF for all k points

 

  getwfk2  1
    iscf2 -2
    nqpt2  0
  tolwfr2  1.0d-22

 

#Dataset 3 : RF at q=0 0 0
 
  kptopt3  2
    iscf3  3
     qpt3  0 0 0
 rfatpol3  1 3
   rfdir3  1 1 1
  rfphon3  1
  tolvrs3  1.0d-10

 

#Dataset 4 : non-SCF at q=1/16 0 0

 

    iscf4 -2
     qpt4  1/16 0.0 0.0
  tolwfr4  1.0d-22

 

#Dataset 5 : RF at q=1/16 0 0
 
  getwfq5  4
    iscf5  3
     qpt5  1/16 0.0 0.0
 rfatpol5  1 3
   rfdir5  1 1 1
  rfphon5  1
  tolvrs5  1.0d-10

 

#Dataset 6 : non-SCF at q=1/8 0 0

 

    iscf6 -2
     qpt6  1/8 0.0 0.0
  tolwfr6  1.0d-22

 

#Dataset 7 : RF at q=1/8 0 0

 

  getwfq7  6
    iscf7  3
     qpt7  1/8 0.0 0.0
 rfatpol7  1 3
   rfdir7  1 1 1
  rfphon7  1
  tolvrs7  1.0d-10

 

#Dataset 8 : non-SCF at q=3/16 0 0

 

    iscf8 -2
     qpt8  3/16 0.0 0.0
  tolwfr8  1.0d-22

 

#Dataset 9 : RF at q=3/16 0 0

 

  getwfq9  8
    iscf9  3
     qpt9  3/16 0.0 0.0
 rfatpol9  1 3
   rfdir9  1 1 1
  rfphon9  1
  tolvrs9  1.0d-10

 

#Dataset 10 : non-SCF at q=1/4 0 0

 

    iscf10 -2
     qpt10  1/4 0.0 0.0
  tolwfr10  1.0d-22

 

#Dataset 11 : RF at q=1/4 0 0

 

  getwfq11  10
    iscf11  3
     qpt11  1/4 0.0 0.0
 rfatpol11  1 3
   rfdir11  1 1 1
  rfphon11  1
  tolvrs11  1.0d-10

 

#Dataset 12 : non-SCF at q=5/16 0 0

 

    iscf12 -2
     qpt12  5/16 0.0 0.0
  tolwfr12  1.0d-22

 

#Dataset 13 : RF at q=5/16 0 0

 

  getwfq13  12
    iscf13  3
     qpt13  5/16 0.0 0.0
 rfatpol13  1 3
   rfdir13  1 1 1
  rfphon13  1
  tolvrs13  1.0d-10

 

#Dataset 14 : non-SCF at q=3/8 0 0

 

    iscf14 -2
     qpt14  3/8 0.0 0.0
  tolwfr14  1.0d-22

 

#Dataset 7 : RF at q=3/8 0 0

 

  getwfq15  14
    iscf15  3
     qpt15  3/8 0.0 0.0
 rfatpol15  1 3
   rfdir15  1 1 1
  rfphon15  1
  tolvrs15  1.0d-10

 

#Dataset 16 : non-SCF at q=7/16 0 0

 

    iscf16 -2
     qpt16  7/16 0.0 0.0
  tolwfr16  1.0d-22

 

#Dataset 17 : RF at q=7/16 0 0

 

  getwfq17  16
    iscf17  3
     qpt17  7/16 0.0 0.0
 rfatpol17  1 3
   rfdir17  1 1 1
  rfphon17  1
  tolvrs17  1.0d-10

 

#Dataset 18 : non-SCF at q=1/2 0 0

 

    iscf18 -2
     qpt18  1/2 0.0 0.0
  tolwfr18  1.0d-22

 

#Dataset 19 : RF at q=1/2 0 0

 

  getwfq19  18
    iscf19  3
     qpt19  1/2 0.0 0.0
 rfatpol19  1 3
   rfdir19  1 1 1
  rfphon19  1
  tolvrs19  1.0d-10

 

#Common data

 

#Definition of the unit cell
acell   3.68  3.68     6.61 angstrom
#rprim  0.866 -0.500   0.000     # It is better to define
#       0.000  1.000   0.000     # the primitive vectors
#       0.000  0.000   1.000     # using rprim
angdeg 90 90 120

 

#Definition of the atom types
ntypat 2          # There are two type of atoms
znucl 41 52       # The keyword "znucl" refers to the atomic number of the
                  # possible type(s) of atom. The pseudopotential(s)
                  # mentioned in the "files" file must correspond
                  # to the type(s) of atom.

 

#Definition of the atoms
natom 3           # There are three atoms
natrd 2           # Reads two atoms
typat 1 2         # type 1 is Nb, type 2 is Te
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
   0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of atom 1.
   1/3  2/3  1/4  # Triplet giving the REDUCED coordinate of atom 2.
                  # Note the use of fractions (remember the limited
                  # interpreter capabilities of ABINIT)

 

spgroup 164       # Spacegroup

 

#Definition of the occupation numbers
occopt 4
tsmear 0.01

 

#Read psp
npsp 2            # Read 2 psp files
ixc 1             # Nb is of type ixc 1. Te is of type ixc 1.
                  # LDA. Nb contains semicores.

 

#Definition of the planewave basis set
ecut 10.0         # Maximal kinetic energy cut-off, in Hartree

 

ngkpt 8 8 4       # Creates a 8x8x4 k-point grid

 

#Definition of the SCF procedure
nstep 250         # Maximal number of SCF cycles

 

#diemac 12.0      # For metals, we use the default 10^6.
nband 35          # nband=nb of electrons in unit cell/2+(20% for metals)
                  # more bands are needed with semicore states