Dear abiniters:
I've done a RF calculation of elastic constant. In the anaddb
output file, there are two warnings:
instr9 : WARNING -
Acoustic sum rule violation met : the eigenvalues of accoustic
mode are too large at Gamma point.
Increase cutoff energy or k-points sampling.
The three eigenvalues are: 6.669281E-02 1.580351E-02
6.669281E-02
instr9 : WARNING -
Unstable eigenvalue detected in force constant matrix at Gamma
point. The system under calculation is physically unstable.
Base on the previous experience, the first warning may be
ignored.
But I have no idea what the second one means. The clamped-ion
and
relaxed-ion elastic tensor are quite strange shown in the attachment
with
the input file.
What's wrong with this calculation?
I appreciate any advice. Thanks a lot in advance.
Sincerely.
Yong Liu
-------------------------------------------------------------------------------------
Yong Liu,
Institute of Inorganic Materials,
Department of Materials Science and Engineering,
Zhejiang University,PR China
Doctoral student
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# Here ABINIT input file
# Input the GS wavefunction and
# Calculate elastic constant
# of PP-PT (No.87, I4/m)
#Test
prtvol 0
prtkpt 0
ndtset 1
#Dataset1: Initial self-consistent run
# irdwfk1 1
# iscf1 3
# kptopt1 1
# tolvrs1 1.0d-18
#Dataset2: Response Function calculation : electric field perturbation and phonons
irdwfk1 1
iscf1 3
kptopt1 2
nqpt1 1
qpt1 0 0 0
rfphon1 1
rfatpol1 1 20
rfstrs1 3
rfdir1 1 1 1
tolvrs1 1.0d-12
#SCF calculation
kptopt 1
kptrlatt -5 -5 -3
-2 -2 3
2 5 0
shiftk 5.0000E-01
5.0000E-01
5.0000E-01
nstep 120
diemac 6.0
#Definition of the planewave basis set
ecut 45.0
nband 88
ecutsm 0.5
#Common Data Definition of the unit cell
acell 1.6683970832E+01 1.6683970832E+01 1.6683970832E+01
rprim -6.9104015593E-01 6.9104015593E-01 2.1195991552E-01
6.9104015593E-01 -6.9104015593E-01 2.1195991552E-01
6.9104015593E-01 6.9104015593E-01 -2.1195991552E-01
typat 1 3 2 2 2 1 3 2 2 2 1 3 2 2 2 1 3 2 2 2
ntypat 3
natom 20
xred 6.4872470792E-01 6.6373918712E-01 3.1246389507E-01
3.5741920514E-01 3.1783170685E-02 3.8920237585E-01
4.9509640059E-02 2.3798128987E-01 2.8749092995E-01
7.1036151449E-01 8.3396059727E-01 5.4432211180E-01
1.0390469327E-01 4.7337848088E-01 5.7728317416E-01
6.6373918712E-01 3.5127529205E-01 1.5014479204E-02
3.1783170688E-02 6.4258079484E-01 6.7436396555E-01
2.3798128987E-01 9.5049035992E-01 1.8847164982E-01
8.3396059727E-01 2.8963848547E-01 1.2359908278E-01
4.7337848087E-01 8.9609530671E-01 3.6947378761E-01
3.5127529206E-01 3.3626081285E-01 6.8753610493E-01
6.4258079483E-01 9.6821682929E-01 6.1079762416E-01
9.5049035992E-01 7.6201871010E-01 7.1250907005E-01
2.8963848548E-01 1.6603940270E-01 4.5567788821E-01
8.9609530671E-01 5.2662151909E-01 4.2271682584E-01
3.3626081286E-01 6.4872470792E-01 9.8498552080E-01
9.6821682929E-01 3.5741920513E-01 3.2563603446E-01
7.6201871011E-01 4.9509640057E-02 8.1152835018E-01
1.6603940271E-01 7.1036151450E-01 8.7640091723E-01
5.2662151911E-01 1.0390469327E-01 6.3052621239E-01
znucl 82 8 22
