[Nexus] unit_cell in NXsample

[Osborn, Raymond]

Coincidentally, I was going to raise this at the next NIAC because of the unit inconsistency and because there are already definitions of all these parameters in the NXcrystal definition, which is what I have been using in my code:

unit_cell_a: NX_FLOAT {units=NX_LENGTH}
Unit cell lattice parameter: length of side a

unit_cell_b: NX_FLOAT {units=NX_LENGTH}
Unit cell lattice parameter: length of side b

unit_cell_c: NX_FLOAT {units=NX_LENGTH}
Unit cell lattice parameter: length of side c

unit_cell_alpha: NX_FLOAT {units=NX_ANGLE}
Unit cell lattice parameter: angle alpha

unit_cell_beta: NX_FLOAT {units=NX_ANGLE}
Unit cell lattice parameter: angle beta

unit_cell_gamma: NX_FLOAT {units=NX_ANGLE}
Unit cell lattice parameter: angle gamma

I suggest we use these in NXsample as well.

Ray


On Sep 17, 2014, at 12:57 PM, Pete Jemian <prjemian at gmail.com> wrote:

> Let's propose Herb's suggestion at the NIAC meeting.
> For now either we leave as-is or adopt the suggestion from Tobias to have two attributes for units, as he stated it.
> 
> On 9/17/2014 12:45 PM, Herbert J. Bernstein wrote:
>> The most common convention for a unit cell is a,b,c in angstroms
>> alpha, beta, gamma in degrees in that order.  However there are
>> lots of other conventions.  There would be less chance of confusion
>> and error with their own units.  Both direct and reciprocal cells are
>> important.  I would suggest long, but unambiguous, names:
>> 
>> cell_length_a, cell_length_b, cell_length_c,
>> cell_angle_alpha, cell_angle_beta, cell_angle_gamma,
>> recip_cell_length_a_star, recip_cell_length_b_star, recip_cell_length_c_star,
>> recip_cell_angle_alpha_star, recip_cell_angle_beta_star,
>> recip_cell_angle_gamma_star
>> 
>> The space group is also important.  For clarity on the above, see
>> IUCr International Tables Volume A (or better, the old Volume I)
>> 
>> On Wed, Sep 17, 2014 at 1:28 PM, Andy Gotz <andy.gotz at esrf.fr> wrote:
>>> On 17/09/2014 19:16, Pete R. Jemian wrote:
>>>> 
>>>> No good answer for now.
>>> 
>>> 
>>> A bit worrying for a fundamental parameter like unit cell isn't it ?
>>> 
>>> Andy
>>> 
>>> --
>>> Save our inboxes!
>>> 
>>> http://emailcharter.org
>>> 
>>> _______________________________________________
>>> NeXus mailing list
>>> NeXus at nexusformat.org
>>> http://lists.nexusformat.org/mailman/listinfo/nexus
>>> 
>> _______________________________________________
>> NeXus mailing list
>> NeXus at nexusformat.org
>> http://lists.nexusformat.org/mailman/listinfo/nexus
>> 
> _______________________________________________
> NeXus mailing list
> NeXus at nexusformat.org
> http://lists.nexusformat.org/mailman/listinfo/nexus

-- 
Ray Osborn, Senior Scientist
Materials Science Division
Argonne National Laboratory
Argonne, IL 60439, USA
Phone: +1 (630) 252-9011
Email: ROsborn at anl.gov