[Pw_forum] Error in routine cdiaghg (427): S matrix not positive definite

[kulwinder kaur]

hello QE user
first i relax struture. then i do 'scf' calculation. these calculation
worked well. after that when i run 'band' calculations the follwing error
occur.

 Error in routine cdiaghg (427):
     S matrix not positive definite


my input file is this
&control
    calculation = 'bands'
    restart_mode='from_scratch',
    prefix='mg2si',
    pseudo_dir = '.'
    outdir='temp'
     verbosity= 'high'
    wf_collect=.true.

 /
&system
    ibrav=  2, celldm(1) =23.9994, nat= 24, ntyp= 2,
    ecutwfc =55.D0, nbnd=64,occupations='smearing', degauss=0.003,
smearing='m-v',
 /
&electrons
 conv_thr    = 1.0D-12
  mixing_beta = 0.5
  diago_full_acc=.true.
 /

ATOMIC_SPECIES
Mg 24.30 Mg.pbe-mt_fhi.UPF
Si 28.08 Si.pbe-mt_fhi.UPF
K_POINTS (tpiba_b)
4
0.0 0.0 0.0    100
1.0 0.0 0.0    100
0.5 0.5 0.5    100
0.0 0.5 1.0    100
ATOMIC_POSITIONS (angstrom)
Si       0.000000000   0.000000000   0.000000000
Mg       1.587490994   1.587490994   1.587490994
Mg       1.587490994   1.587490994   4.762472983
Si      -3.174981988   3.174981988   0.000000000
Mg      -1.587490994   4.762472982   1.587490994
Mg      -1.587490994   4.762472982   4.762472983
Si       0.000000000   3.174981988   3.174981988
Mg       1.587490994   4.762472982   4.762472982
Mg       1.587490994   4.762472982   7.937454971
Si      -3.174981988   6.349963976   3.174981988
Mg      -1.587490994   7.937454970   4.762472982
Mg      -1.587490994   7.937454970   7.937454971
Si      -3.174981988   0.000000000   3.174981988
Mg      -1.587490994   1.587490994   4.762472982
Mg      -1.587490994   1.587490994   7.937454971
Si      -6.349963976   3.174981988   3.174981988
Mg      -4.762472982   4.762472982   4.762472982
Mg      -4.762472982   4.762472982   7.937454971
Si      -3.174981988   3.174981988   6.349963976
Mg      -1.587490994   4.762472982   7.937454970
Mg      -1.587490994   4.762472982  11.112436959
Si      -6.349963976   6.349963976   6.349963976
Mg      -4.762472982   7.937454970   7.937454970
Mg      -4.762472982   7.937454970  11.112436959


please tell me where is problem in my input file?
-- 
Regards
Kulwinder Kaur
Research scholar (CSIR)
Physics Department
Panjab University Chandigarh.
India
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