I have an input file to calculate phonon frequencies at Gamma as follows:
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ndtset 2 jdtset 1 2
#Ground state calculation
kptopt1 1 # Automatic generation of k points, taking
# into account the symmetry
tolvrs1 1.5d-24 # SCF stopping criterion 6.5
iscf1 7 # Self-consistent calculation, using algorithm 5
#Response-function calculation, with q=0
rfphon2 1 # Will consider phonon-type perturbation
rfatpol2 1 4 # All the atoms will be displaced
rfdir2 1 1 1 # Along all reduced coordinate axis
nqpt2 1 # One wavevector is to be considered
qpt2 0 0 0 # This wavevector is q=0 (Gamma)
kptopt2 2 # Automatic generation of k points, taking
# into account the time-reversal symmetry only
tolvrs2 1.0d-22 # SCF stopping criterion 4.0
iscf2 7 # Self-consistent calculation, using algorithm 5
getwfk2 1 # Read the ground-state wavefunctions
acell 6.0445443963E+00 6.0445443963E+00 9.8221745078E+00
angdeg 90.000 90.000 120.000
spgroup 186
# Definition of the atom
ntypat 2 # Two types of atoms
znucl 31 7 # Ga and N atomic numbers of the
natom 4 # There are four atoms in a cell
typat 1 1 2 2 # Type 1 is Ga, type 2 is N
xred # Fractional coordinates
1/3 2/3 0.00
2/3 1/3 0.50
1/3 2/3 3.7747675599E-01
2/3 1/3 8.7747675599E-01
#Gives the number of band, explicitely (do not take the default)
nband 8
## Definition of XC functional and planewave basis set
ixc 11 # Teter XC functional
ecut 30 # Kinetic energy cut-off (in Ha)
ecutsm 0.5
dilatmx 1.05
ngkpt 5 5 4
nshiftk 1
shiftk 0.0 0.0 0.5
#Definition of the SCF procedure
nstep 700 # Maximal number of SCF cycles
diemac 10.0
ntime 100
tolmxf 1.0d-9
The first issue worried me is the warning in output file. Below is part of output file with warning hdr_check: WARNING -
-P-0000 input nkpt= 50 not equal disk file nkpt= 10
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-P-0000 ================================================================================
-P-0000
-P-0000 - hdr_check: checking restart file header for consistency -
-P-0000
-P-0000
-P-0000 current calculation restart file
-P-0000 ------------------- ------------
-P-0000
-P-0000 calculation expects a wf_planewave | input file contains a wf_planewave
-P-0000 . ABINIT code version 6.4.2 | ABINIT code version 6.4.2
-P-0000 . date 20110409 bantot 400 natom 4 | date 20110409 bantot 80 natom 4
-P-0000 nkpt 50 nsym 12 ngfft 32, 32, 54 | nkpt 10 nsym 12 ngfft 32, 32, 54
-P-0000 ntypat 2 ecut_eff 33.0750000 | ntypat 2 ecut_eff 33.0750000
-P-0000 usepaw 0 | usepaw 0
-P-0000 usewvl 0 | usewvl 0
-P-0000 rprimd: | rprimd:
-P-0000 6.0445444 0.0000000 0.0000000 | 6.0445444 0.0000000 0.0000000
-P-0000 -3.0222722 5.2347290 0.0000000 | -3.0222722 5.2347290 0.0000000
-P-0000 0.0000000 0.0000000 9.8221745 | 0.0000000 0.0000000 9.8221745
-P-0000
-P-0000 hdr_check: WARNING -
-P-0000 input nkpt= 50 not equal disk file nkpt= 10 If i set up k-point grid with ngkpt 5 5 4; nshiftk 1; shiftk 0.0 0.0 0.5 there is nkpt=10. But left column says there 50! Why? And why bantot = 400? Please could some one clear it to me, many thanx in any advance!
The second issue is acoustic modes. Namely frequencies in Gamma point as a result of calculations. The abinit code gives the following frequencies:
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Phonon frequencies in cm-1 :
- -1.827276E+01 2.430194E+01 2.430194E+01 1.409284E+02 1.409284E+02-18cm-1, whatta? It is definitely wrong frequencies. Why it's so high and even negative? Am I lost something? Thank you for reading.
