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[occupierliu@yahoo.com.cn]

Dear all:
    I'm trying to calculate the elastic constants of PbTiO3(P4mm) and in the 
output file of anaddb there is a warning message:
phonon modes warning- :
accoustic 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:    2.480398E-04    3.065292E-05    2.480407E-04.

So I increased the ecut from 45H to 55H and ngkpt from 75 to 115 while the 
total energe decrease from -1.65976000880566E+02H to -1.6598600852E+02H and 
-1.6597872349E+02, respectively. I think the convergence is good enough, but 
unfortunately the warning message is still there only the the eigenvalues 
change a litte:
ecut 45 and ngkpt 115    2.480462E-04    3.065251E-05    2.480464E-04
ecut 55 and ngkpt 75     1.718815E-04    3.278633E-06    1.718815E-04.

Should I keep increaseing the ecut and ngkpt untill this warning disappears 
or there this some other parameters I can change? Because the large ecut and 
ngkpt cause a huge time-consuming computation work.
    Thanks a lot in advance.

# Here My input file for ABINIT 4.6.4
# PbTiO3 (No.99, P4mm)

   ndtset     2

#Dataset1: Initial self-consistent run
    iscf1     5
  kptopt1     1
  tolvrs1     1.0d-18

#Dataset2: Response Function calculation
  getwfk2    -1
    iscf2     5
  kptopt2     2
    nqpt2     1
     qpt2     0 0 0 
  rfphon2     1
 rfatpol2     1 5
  rfstrs2     3
   rfdir2     1 1 1
  tolvrs2     1.0d-12
 
#SCF calculation
    ngkpt     10 10 10
    nband     22

#Definition of the planewave basis set
     ecut     45.0
   ecutsm     0.5

#Definition of the SCF procedure
    nstep     100
   tolvrs     1.0d-18 
   diemac     6.0 
    
#Common Data Definition of the unit cell
    acell     7.3016242907  7.3016242907  7.5097985279
    rprim     1.0     0.0     0.0
              0.0     1.0     0.0
              0.0     0.0     1.0
   ntypat     3
    znucl     82 8 22
    natom     5
    typat     1 3 2 2 2
     xred     0.0000000000E+00  0.0000000000E+00  0.0000000000E+00
              5.0000000000E-01  5.0000000000E-01  4.6901801570E-01
              5.0000000000E-01  5.0000000000E-01  9.2453581448E-01
              5.0000000000E-01  8.7581154020E-47  4.0875625165E-01
              0.0000000000E+00  5.0000000000E-01  4.0875625165E-01