[Pw_forum] Question about tests

Paolo Giannozzi giannozz at nest.sns.it
Tue Jan 15 16:34:25 CET 2008

On Jan 15, 2008, at 14:30 , Andreas Kissavos wrote:

> everything is identical up to the inversion of the dynamical matrix

the dynamic al matrix is diagonalized, not inverted

> My are 0.101977 [THz] while the reference is 0.093301 [THz].
> Note that everything is identical (to 6 decimals at least) before  
> this.

in the specific case: those frequencies should be exactly zero, so
I wouldn't mind too much if the "almost zero" you get is not exactly
the same "almost zero" of the examples (the reason for nonzero
acoustic frequencies is explained in the user guide). In general:
it would be nice to have reproducibility of the printed figures, but
I am afraid it is a lost cause: there are too many places where
small differences show up for no apparent reason. If anybody has
any idea on possible actions, he/she is welcome.

Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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