The ABINIT Users Mailing List ( CLOSED )

[Yong Liu <occupierliu@yahoo.com.cn>]

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

Attachment: ANAOutputFiles.out
Description: 3554782407-ANAOutputFiles.out