calculation of a x-ray structure

[Jörg Saßmannshausen]

Dear all,

when I am usually calculate structures from the data I am obtaining via a x-
ray analysis, i.e. from the CIF file, I simply take the single molecule and run 
that via some DFT functional. No periodic boundries, if there are two 
molecules in the unit cell I simply pick one. 

However, to find out whether a specific effect I am seeing is due to crystal 
packing or not, I actually want to calculate the complete unit cell, which 
contains two molecules, and I want to calculated it as a lattice, i.e. one 
more cell in each direction. This way, I hope, I would see whether it is due 
to crystal packing effects what I am observing, or not. 

>From the CIF file I know it is a triclinic cell and I also know the geometric 
parameters, i.e. a,b,c and the angles.

If I plug that into the subsys section of the input file and I am using the MT 
POISSON_SOLVER, what else do I need to bear in mind? 
Does that actually make sense what I am trying to do or is that a waste of my 
time? I never done solid state calculations as I am more a single molecule 
person so your advice here would be much appreciated. 

Please let me know if you got any further questions.

All the best from a dull London

Jörg

-- 
*************************************************************
Dr. Jörg Saßmannshausen, MRSC
University College London
Department of Chemistry
20 Gordon Street
London
WC1H 0AJ 

email: j.sassma... at ucl.ac.uk
web: http://sassy.formativ.net

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html
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