[CP2K:1571] UNIT in &CELL and UNIT for output

[Toon Verstraelen]

Hi Teo,

Your efforts to get the dinosaurs out of the code are apreciated for sure. I'm a 
bit worried about the configurable unit for the output files. This can be nasty, 
e.g. when one has to post-process someone else's output files. Most of the times 
this is a total disaster, certainly when I'm not totally sure about the units in 
the output files.

Are there plans for a standardized binary output format that contains all the 
simulation data in a fixed unit, e.g. atomic units. This would avoid a lot of 
misery. Another possible solution would be a standardized header that contains 
the unit conventions used in the rest of the output file. The latter is maybe a 
bit trickier? Are there any long term plans in this direction?

cheers,

Toon


Teodoro Laino wrote:
> Dear All,
> 
> A major rearrangement of the UNIT keyword in the CELL section was required.
> The reason is that, the UNIT keyword was to be considered an old 
> duplicate compared to the more
> advanced way we can treat units (i.e. specifying them within square 
> brackets []), and this was posing
> severe issues, more technical (code specific) than user perspective.
>  
> Therefore this is how the code has been updated:
> 1) UNIT keyword has been deleted from CELL section
> 2) keyword A,B,C and ABC have now units (to specify a cell in bohr 
> therefore is enough to
>     input something like ABC [bohr] x y z)
> 3) the units for the coord section can be specified now with two 
> specific keywords in &COORD section
>     COORD%UNIT  (by default angstrom)
>     COORD%SCALED (by default set to FALSE)
>     The first one accept a string (all units defined in CP2K can be 
> input). The second one is a boolean.
>     The units for the cell and for the coordinates have been now fully 
> disentangled (you can use all kind
>      of combinations you like)
> 
> The sad part:
> This change will break unavoidably all old input files, but the 
> modifications to be done to make them compatible
> with the new version are minor (just follow the few steps above).
> 
> The innovation:
> Moreover, since quite few people ask from time to time about units of 
> output quantities, the last commit introduces, as well, the possibility 
> to specify a unit of measure for quantities in output.
> As you can imagine this would require a huge amount of work and the plan 
> is to do it slowly.
> Therefore at the moment very few print_key support the UNIT keyword. 
> Possible requests to extend it
> to other print_keys are well accepted and encouraged. All 
> requests/comments can be posted on this thread.
> 
> Luckily this should be one of the last dinosaurs in CP2K (i.e. there 
> should not be other major changes
> that break so deeply the compatibility between CVS shapshots).
> My apologies for this inconvenience.
> Teo
> 
> > 


-- 
ir. Toon Verstraelen
Center for Molecular Modeling
Ghent University
Proeftuinstraat 86
B9000 Gent
Belgium
Tel: +32 9 264 65 56
E-mail: Toon.Ver... at UGent.be
http://molmod.UGent.be/
http://molmod.UGent.be/code/
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