Crystallography Online: the website of the International Union of Crystallography

David, Brian:

    I'm just preparing four proposed items for the CIFcore dictionnary.

    The DDL1 core dictionnary does not give any clue about how to 
indicate the units of dimensionless quantities. Is there any official 
policy?  I remember reading in the thick wad of papers that execsec 
distributes for the general assembly that the BIPM is discussing a 
proposition allowing dimensionless quantities to have an official SI "unit".

H.

> data_units
>     _definition
> ;              A unique code which identifies the units of the defined data
>                item. A description of the units is provided in _units_detail.
> ;
>     _name                      '_units'
>     _category                    units
>     _type                        char
>     loop_ _example
>           _example_detail         K    'kelvins'
>                                   C    'degrees Celsius'
>                                   rad  'radians'
>                                   e    'electrons'
>                                   V    'volts'
>                                   Dal  'daltons'
>                                   m    'metres'
>                                   kg   'kilograms'
>                                   s    'seconds'
> 
> data_units_detail
>     _definition
> ;              A description of the numerical units applicable to the defined
>                item and identified by the code _units.
> ;
>     _name                      '_units_detail'
>     _category                    units
>     _type                        char