Re: PowderCell and O2-

Armel Le Bail ( armel@fluo.univ-lemans.fr )
Fri, 04 Sep 1998 09:52:59 +0200

<x-rich>>I tried to use PowderCell 1.0 to draw the crystallographic structure
and

>look at possible modifications in the pattern due to slight change in
ion

>positions, but I did not succeed because the program does not accept
the

>2- state for the oxygen!

>Does anyone know about this strange feature? Any hint?

Even the International Tables for Crystallography do not give the

oxygen 2- state... Probably some influent guy who does not believe to

ionized compounds ? Anyway, people generally use the parametrized

values :<fontfamily><param>Courier New</param><smaller> 4.758 7.831
3.637 30.05 0. 0. 0. 0. 1.594

</smaller></fontfamily>taken from : T. Suzuki, <italic>Acta
Cryst</italic>. <bold>13</bold> (1960) 279.

A question now for phosphates. International Tables have only

neutral P X-ray scattering factors. So, what is the recommendation

for a compound like Li6P6O18 ? Li+, P and O2- or all neutral

atoms ?-).

Armel

PS : Matteo, the http://bragg.ing.unitn.it/sizestrain/ page announced

in the CPD Newsletter 20 is still empty...

Armel Le Bail - Université du Maine, Laboratoire des Fluorures,

CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France

http://fluo.univ-lemans.fr:8001/

http://www.cybercable.tm.fr/~cristal/

Tel: (33) 02 43 83 33 47

</x-rich>