[Pw_forum] Tips for vc-relax when far from equilibrium

[Brad Malone]

Hi, I am trying to relax (via vc-relax) structures that are, at least most
likely, very far from equilibrium. I was wondering if there were any tips on
how to make this more robust, as I'm currently experiencing frequent crashes
for these systems.

The main problem I'm having is shown below:

 After a *couple successful relaxation steps*, I'll find the following

     extrapolated charge    6.83616, renormalised to    8.00000
>
>      total cpu time spent up to now is    614.83 secs
>
>      per-process dynamical memory:    28.6 Mb
>
>      Self-consistent Calculation
>
>      iteration #  1     ecut=    20.00 Ry     beta=0.10
>      CG style diagonalization
>  WARNING pzsteqr, convergence not achieved INFO =            3
>      c_bands:  4 eigenvalues not converged
>  WARNING pzsteqr, convergence not achieved INFO =            3
>      c_bands:  4 eigenvalues not converged
>  WARNING pzsteqr, convergence not achieved INFO =            3
>      c_bands:  4 eigenvalues not converged
>      c_bands:  1 eigenvalues not converged
>
 4 processes killed (possibly by Open MPI)
>


So the first thing is that my extrapolated charge is very far off from the
value of 8 expected (I have two Si atoms in the unit cell). Secondly, the
self-consistent calculation fails and kills the job. I've tried using
davidson diagonalization as well and it also crashes.

Any suggestions on how I might avoid this? Thanks for your time.

Best,
Brad
UC Berkeley
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