[Pw_forum] questions on molecular dynamics example

Xunlei Ding ding at sissa.it
Wed Dec 27 10:55:43 CET 2006

Dear Eduardo

I am also interested in your questions.

I think extrapolation will accelerate scf calculations in some cases, but not in
all case. It is more suitable for the system in which the ionic positions
change little between two MD steps or optimization steps in 'relax'

Yours sincerely,

Quoting Eduardo Ariel Menendez P <emenendez at macul.ciencias.uchile.cl>:

> Hi Paolo,
> I saw these options in the examples of molecular dynamics woth PW. There
> is few information in the Doc files and the forum.
>     pot_extrapolation='second-order',
>     wfc_extrapolation='second-order',
> I guessed that extrapolation options would reduce the number of
> self-consistent steps in MD steps. However, in the case I am running
> (CdTe) he number of self consistent steps at each ionic steps averages
> 16, regardless of the extrapolation keywords.
> Other keyword that I see in the examples is
>     disk_io='high',etc,
> Is this keyword useful to improve the efficiency of molecular dynamics?
> Other issue. I had this error in step 90
>      iteration #  4     ecut=    30.00 Ry     beta=0.70
>      Davidson diagonalization with overlap
>      from rdiaghg : error #      1986
>      info =/= 0
> Consulting the manual and the forum I see that it is difficult to find
> the cause, and that the first choice is restart
> and see what happens. I did it and the calculation just continued without
> error. ?Does it allows to discard the possible cause of bad
> pseudopotential, and bug of the lapack algorithm, in favor of buggy mahine
> optimization of lapack (MKL) ?
> Thanks
> Eduardo
> Eduardo A. Menendez Proupin
> Department of Physics
> Faculty of Science
> University of Chile
> Las Palmeras 3425
> Ñuñoa, Santiago
> Chile
> Phone: 56+2+978 74 11
> http://fisica.ciencias.uchile.cl/~emenendez/
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