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From: "Stefan Beyreuther" <stefan-: at :-indi.aci.uni-heidelberg.de>
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Date: Tue, 10 Sep 1996 16:29:26 -0600
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To: CHEMISTRY ":at:" www.ccl.net
Subject: Wilson Out-Of-Plane Coordinate
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	Dear CCLers

	Could someone explain me what exactly the Wilson out-of-plane
	coordinate is?

	It is used in forcefields like CFF91 or ESFF (Discover, MSI).
	The functional form is

		___
		\  '    2
		 >   K X
		/__,  i
		 i


	The manual only says:

	"The functional form of the out-of-plane energy ..., where the
	coordinate is an average of the three possible angles associated
	with the out-of-plane center. The single parameter that is
	associated with the central atom is a fit quantity."

	I have the corresponding reference

	Wilson, E. B.; Decius, J. C.; Cross, P. C. Molecular Vibrations,
	Dover, New York (1980).

	but we don't have the book here.

	Thanks a lot
	Stefan


	Stefan Beyreuther
                                          Anorganisch-Chemisches Institut
        fon +49-6221-548634                       Universitaet Heidelberg
        fax +49-6221-545707                              69120 Heidelberg
        e-mail stefan#* at *#indi.aci.uni-heidelberg.de                  Germany