[QE-users] S matrix not positive definite

[Ubaid Mohd]

Dear Experts,
 I am doing a calculation related to bilayer phosphorene. I have
successfully done vc relaxation and bandstructure calculations. When I am
doing the nscf calculation using the same outdir & prefix flag, I am
getting the error.........

     Computing kpt #:    45
     total cpu time spent up to now is     4384.4 secs

     Computing kpt #:    46
     c_bands:  2 eigenvalues not converged
     total cpu time spent up to now is     4497.2 secs

     Computing kpt #:    47
     c_bands:  2 eigenvalues not converged
     total cpu time spent up to now is     4611.2 secs

     Computing kpt #:    48
     c_bands:  4 eigenvalues not converged
     total cpu time spent up to now is     4727.0 secs

     Computing kpt #:    49
     c_bands:  2 eigenvalues not converged
     total cpu time spent up to now is     4840.0 secs

     Computing kpt #:    50
     c_bands:  2 eigenvalues not converged
     total cpu time spent up to now is     4946.0 secs

     Computing kpt #:    51
     c_bands:  2 eigenvalues not converged
     total cpu time spent up to now is     5053.2 secs

     Computing kpt #:    52

     Error in routine cdiaghg (904):
     S matrix not positive definite
      stopping ...

I search the solution of related problem on google in which error is due to
"atoms are very close to each other" but, if atoms are very close to each
other, why I am getting the optimized structure and the correct band gap?
How to sort out this problem to proceed the further calcultions like dos,
pdos and charges etc.

Thanks and regards

*Mohammad Ubaid*
*PhD Research Scholar*
*Department of Physics*
*Jamia Millia Islamia University*
*New Delhi - 110025*
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