ABINIT Discussion Forums

Dear users and developers,
I am facing a problem calculating the phonon frequencies for phonons.
When I used an old abinit version (Version 6.4.3) I have a negative frequency at the G-point.
I then used a newer version (Version 6.8.2) with a new setting of the phonon-calculations (like in t35.in and t78.in):
# phonons
prtvol 3
ndtset 48
udtset 24 2
# ground state
#Dataset 1 : SCF
getden 11
getwfk 11
kptopt 3
# Response Function calculation
# qpt generation
Chksymbreak 0
nqpt 1
qptopt 1
ngqpt 14 14 1
nshiftq 1
shiftq 0.0 0.0 0.0
iqpt:? 1
iqpt+? 1
#Dataset 11 : SCF
getden11 0
getwfk11 0
iscf11 5
nqpt11 0
prtden11 1
###############
#Dataset 2 : phonon at gamma
getwfq12 0
##################

#Dataset ?1 : non-SCF
iscf?1 -2
tolwfr?1 1.0d-22
#Dataset ?2 : RF
getwfq?2 -1
rfatpol?2 1 1
rfdir?2 1 1 1
rfphon?2 1
tolvrs?2 1.0d-18
#######################################################################
#Common input variables
#######################################################################

acell 4.6411685 4.6411685 12
xred 0.0000000000E+00 0.0000000000E+00 0.0
1/3 1/3 0.0

rprim 1.0 0.0 0.0 # Hex. primitive vectors(to be scaled by acell)
0.5 0.8660254037844386 0.0
0.0 0.0 1.0

#Definition of the atom types
ntypat 1 # There are two types of atoms
znucl 6 # The keyword "zatnum" 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 2
typat 1 1
ngkpt 14 14 1
nshiftk 1 # Use one copy of grid only (default)
shiftk 0.0 0.0 0.0 # This choice of origin for the k point grid
# preserves the hexagonal symmetry of the grid,
# which would be broken by the default choice.
nband 10
nbdbuf 4
occopt 3
tsmear 0.005

#Definition of the planewave basis set
ecut 35.0 # Minimal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure
nstep 50 # Maximal number of SCF cycles
diemac 4.50
########################################
and even There I got a higher negative frequency at G-point! and the overall band dispersion looks really poor!! and really strange........I checked this for different k-sampling.
What I am missing exactly?
Many thanks,
Samir