Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Imgcif-l] ImgCIF Densiry Maps

David Brown wrote:
> Joe Krahn wrote:
> 
>> What about equation forms? It is important to define more than just the
>> space group, because non-standard settings can be useful in some cases.
>>
> The Hall symbol is a space group name (symbol) that specifies all
> possible settings of the 230 regular space groups.  It can easily be
> expanded into the list of the expressions of symmetry operations.
> 
I was looking over the Hall notation. If I understand it right, it only
defines origin choices which are symmetry equivalents of the normal
origin choice. There are cases where it is useful to shift a C2221
origin to align symmetry operators with those of P212121. I don't think
the standard Hall notation handles this sort of case, at least not as
tabulated in the International tables.

The other issue is that interactions may need to define a specific
symmetry operation. Is there a standard way to derive the symmetry
operators in a specific order from Hall notation?

Joe
_______________________________________________
imgcif-l mailing list
imgcif-l@iucr.org
http://scripts.iucr.org/mailman/listinfo/imgcif-l

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Science Council (admitted 1947). Member of CODATA, the ISC Committee on Data. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

International Science Council Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.

Useful links