Re: [sdpd] Value of Z for P2/M space group?

["Amir Mahmoudkhani" <amir...@ucalgary.ca>]

Hello,

Z is absolutely restricted by symmetry, thus Z = 2 or 4 are the most
possible and frequent ones for such a lattice. For same reason, one may
even find higher orders (that needs a good reason, like difference in
conformational geometry or type of intermolecular interactions). Again,
because of symmetry restrictions, Z = 5 (or 1.25 times in asymmetric unit)
is rather impossible! There are some articles in Acta Cryst. B discussing
on issue of higher number of unit formula (Z) which are very good to read.

Some programs may suggest such a number at first, because of the given
(input) formula) is taken into calculations [F(000)]. But, mostly you will
find solvent residues in the crystalline lattice which were not considered
at first, causing this problem.

Yours,
Amir

> Dear All
>
> I would like to ask about the value of Z (number of
> unit formula) for space group P2/M
> is it possible to be Z=5 or it can be only 2 OR 4?
> (the value of Z will depend on the space group or it
> can take any whole number 1,2,3,4,5,.....)
> Thank you
> hamid
>
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-----------------------------
Amir H. Mahmoudkhani, PhD
Department of Chemistry
University of Calgary
Calgary, AB, T2N 1N4, Canada
Tel.: (+1)403 220 5344 (Lab)
Tel.: (+1) 403 220 7777 (Office)
Fax: (+1)403 289 9676
E-mail: amir...@ucalgary.ca
URL: www.ucalgary.ca/~amir




 
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