[Pw_forum] S matrix not positive definite in Fermi surface calculation

[Uri Argaman]

Dear QE users and developers

I do Fermi surface calculation and I got an error message:
"Error in routine cdiaghg (126):
  S matrix not positive definite"
I note that in some crystal geometries I got this message and in other
geometries I didn't got this error and the Fermi surface looks fine and
reasonable.

This is the input file:
&control
    calculation='bands'
    restart_mode='from_scratch',
    prefix='ti',
    pseudo_dir='/home/uriargaman/QE/espresso-5.1/pseudo/',
    outdir='/home/uriargaman/tmp31971/TMP_FS/',
    tstress = .true. ,
    tprnfor = .true. ,
    verbosity='high',
 /
 &system
    ibrav=  4, celldm(1) =5.48090015121, celldm(3) =1.6120416161 , nat= 2,
ntyp= 1,
    ecutwfc =50,ecutrho=500,
    occupations='smearing', smearing="methfessel-paxton", degauss=0.01,
     nbnd=16
 /
 &electrons
    conv_thr =  1.0d-9,
    electron_maxstep=1000
    mixing_beta = 0.7d0,
 /

ATOMIC_SPECIES
   Ti   47.9  Ti.bp-sp-van_ak.UPF
ATOMIC_POSITIONS (crystal)
   Ti      0.666666666    0.333333333    0.250000000    0  0  0
   Ti      0.333333333    0.666666666    0.750000000
K_POINTS
  4913
....

What can be the problem and how can I solve it?

Thank you in advance
Uri Argaman
Ben-Gurion University
Israel
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20150121/7fb75681/attachment.html>