From owner-chemistry@ccl.net Wed Aug 13 09:56:00 2008
From: "Justin Finnerty justin.finnerty-x-uni-oldenburg.de" <owner-chemistry(-)server.ccl.net>
To: CCL
Subject: CCL: Crysallographic structure Vs optimized
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X-Original-From: Justin Finnerty <justin.finnerty(~)uni-oldenburg.de>
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Date: Wed, 13 Aug 2008 14:08:49 +0200
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Sent to CCL by: Justin Finnerty [justin.finnerty#uni-oldenburg.de]
Crystal v Calc.

One issue to be aware of is that the X-ray structure shows a time
averaged structure. For example triphenylene is seen as planar at room
temperature by X-ray, however this is the time-average of two twisted
conformers. When the X-ray is taken at low temperature the two
conformers can no-longer interconvert and you can detect the two
structures.

This is not usually a problem and is generally detected because the
X-ray structure is calculated/predicted as close to a transition state
between two conformers.

Cheers
	Justin

-- 
Dr Justin Finnerty
Rm W3-1-165         Ph 49 (441) 798 3726
Carl von Ossietzky Universität Oldenburg