The ABINIT Users Mailing List ( CLOSED )

[fliu@lsec.cc.ac.cn]

Dear all,
  I'm a graduate student and my major is mathematics. 
I have computed the correct phonon band structure of 
2D graphite sheet by ABINIT following the Lesson RF2.
It is a exciting thing for me. 
  Now I want to stretch the 2D graphite sheet in y-direction
and draw the corresponding phonon band structure. The
structure is not hexagonal but centred rectangular. 
Then how should I choose shiftk?
   If I still use nshift 1  shiftk 0 0 0.5 , then there 
will be negative frequency. 
   My input file is as follows:
  
#computation of the phonon spectrum

   ndtset   23
#Set 1 : ground state self-consistency

  getwfk1   0            # Cancel default
  kptopt1   1            # Automatic generation of k points, taking
                         # into account the symmetry
    nqpt1   0            # Cancel default
  tolvrs1   1.0d-15      # SCF stopping criterion (modify default)
  rfphon1   0            # Cancel default
 
#Q vectors for all datasets

#Complete set of symmetry-inequivalent qpt chosen to be commensurate
# with kpt mesh so that only one set of GS wave functions is needed.
#Generated automatically by running GS calculation with kptopt=1,
# nshiftk=0, shiftk=0 0 0 (to include gamma) and taking output kpt set
# file as qpt set. Set nstep=1 so only one iteration runs.

     nqpt   1            # One qpt for each dataset (only 0 or 1 allowed)
                         # This is the default for all datasets and must
                         #  be explicitly turned off for dataset 1.

     qpt2   0.00000000E+00  0.00000000E+00  0.00000000E+00
     qpt3   0.00000000E+00  0.00000000E+00  0.00000000E+00
     qpt4   2.50000000E-01  0.00000000E+00  0.00000000E+00
     qpt5   5.00000000E-01  0.00000000E+00  0.00000000E+00
     qpt6   2.50000000E-01  2.50000000E-01  0.00000000E+00
     qpt7   5.00000000E-01  2.50000000E-01  0.00000000E+00
     qpt8  -2.50000000E-01  2.50000000E-01  0.00000000E+00
     qpt9   5.00000000E-01  5.00000000E-01  0.00000000E+00
     qpt10  0.00000000E+00  0.00000000E+00  2.50000000E-01
     qpt11  2.50000000E-01  0.00000000E+00  2.50000000E-01
     qpt12  5.00000000E-01  0.00000000E+00  2.50000000E-01
     qpt13  2.50000000E-01  2.50000000E-01  2.50000000E-01
     qpt14  5.00000000E-01  2.50000000E-01  2.50000000E-01
     qpt15 -2.50000000E-01  2.50000000E-01  2.50000000E-01
     qpt16  5.00000000E-01  5.00000000E-01  2.50000000E-01
     qpt17  0.00000000E+00  0.00000000E+00  5.00000000E-01
     qpt18  2.50000000E-01  0.00000000E+00  5.00000000E-01
     qpt19  5.00000000E-01  0.00000000E+00  5.00000000E-01
     qpt20  2.50000000E-01  2.50000000E-01  5.00000000E-01
     qpt21  5.00000000E-01  2.50000000E-01  5.00000000E-01
     qpt22 -2.50000000E-01  2.50000000E-01  5.00000000E-01
     qpt23  5.00000000E-01  5.00000000E-01  5.00000000E-01

#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
  tolvrs2   0.0        # Cancel default for d/dk
  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 2         # Treat displacements of all atoms
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-8     # This default is active for sets 3-10

#######################################################################
#Common input variables

#Definition of the unit cell
    acell   2*4.91030168 6.417747        
    angdeg  90.0d0 90.0d0 70.0d0

#Definition of the atom types
   ntypat   1        
    znucl   6        # The keyword "znucl" refers to the atomic number of the 
carbon
                      # 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   2         # There are two atoms
    typat   1 1       # carbon
    xred 0.0 0.0 0.0                         
         1.0/3.0 1.0/3.0 0.0

#Gives the number of band, explicitely (do not take the default)
  #  nband   6       

#Exchange-correlation functional

      ixc   1             # LDA Teter Pade parametrization

#Definition of the planewave basis set

     ecut   15.0           # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
##note here
    ngkpt   4  4  4          
    nshftk  1
    shiftk  0. 0. 0.5

#Definition of the SCF procedure
     iscf   5          # Self-consistent calculation, using algorithm 5
    nstep   50       # Maximal number of SCF cycles
   diemac   12.0        # Although this is not mandatory, it is worth to
                       # precondition the SCF cycle. The model dielectric
                       # function used as the standard preconditioner
                       # is described in the "dielng" input variable section.
                       # The dielectric constant of AlAs is smaller that the 
one of Si (=12).

  Really need your help! Thank you.

  Best Wishes,
  Fang Liu