SUMMARY: Wilson Out-Of-Plane Coordinate
Dear CCLers
A week ago I asked the following question:
> 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.
The answers I received are appended.
Thanks a lot folks.
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
On Sep 10, 6:41pm, Ernst U. Wallenborn wrote:
> Subject: Re: CCL:Wilson Out-Of-Plane Coordinate
>
> Hi,
>
>
> i think you are referring to what is called term (4)
> of the cvff91 forcefield in the Discover manual.
> Wilson, Decius and Cross say:
>
> -----quote-----
> 3 1"
> / theta `
> / `
> 1------4 phi_1 1-------4----------2,3
> \
> \
> 2
>
> The basic definition of the angle involved may be given as
>
> e_42 x e_43
> sin theta =---------------- * e_41
> sin phi_1
> -----unquote-----
>
> i.e. the angle is defined as the one between the bond and the plane
> formed by the three other atoms. Since there are three posssibilities
> to choose (atoms 1, 2, 3) Discover takes an average and uses this
> for the calculations.
>
> Hope this helps
>
>
> --
> Ernst-Udo Wallenborn
> Laboratorium fuer Physikalische Chemie
> ETH Zentrum
> CH-8092 Zuerich
>
>-- End of excerpt from Ernst U. Wallenborn
On Sep 10, 12:42pm, Peter Shenkin wrote:
> Subject: CCL:Wilson Out-Of-Plane Coordinate
> On Sep 10, 4:29pm, Stefan Beyreuther wrote:
> > Subject: CCL:Wilson Out-Of-Plane Coordinate
> > Could someone explain me what exactly the Wilson out-of-plane
> > coordinate is?
>
> If A, B and C are connected to a common "central" atom, D, then
> the angle that the AD vector makes with the BDC plane is a Wilson
> angle. The angle that the BD vector makes with the ADC plane
> is another one.
>
> MMFF (Tom Halgren's Merck Molecular Force Field) also uses these.
>
> -P.
>
> --
> ****** ********** In Memoriam, Bill Monroe, 1911 - 1996 ******************
> * Peter S. Shenkin, Chemistry, Columbia U., 3000 Broadway, Mail Code 3153,*
> ** NY, NY 10027; shenkin #*at*# columbia.edu; (212)854-5143; FAX:
678-9039 ***
> MacroModel WWW page: http://www.cc.columbia.edu/cu/chemistry/mmod/mmod.html
>
>-- End of excerpt from Peter Shenkin
On Sep 11, 10:32am, Tom Sundius U of Helsinki +358 0 1918339 wrote:
> Subject: CCL:Wilson Out-Of-Plane Coordinate
>
> > Could someone explain me what exactly the Wilson out-of-plane
> > coordinate is?
> ...
> > 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.
>
> Another reference, which may be very helpful, is
> S. Califano: Vibrational States, J. Wiley & Sons, London (1976)
> ISBN 0-471-12996-8 (there may be a new edition of this useful book)
> Chapter 4 of this book deals with the Wilson internal coordinates.
>
> Sometimes the out-plane bend coordinate is also defined as
"impromper
> torsion" which involves the dihedral angle between two adjoining
planes.
> The difference between the two definitions is, however, insignificant
for
> an (almost) planar configuration.
>
> +-----------------------------------------------------------------------+
> ! Tom Sundius, Dept. of Physics Internet: Tom.Sundius #*at*# Helsinki.fi
!
> ! University of Helsinki, Finland sundius #*at*# phcu.helsinki.fi
!
> +-----------------------------------------------------------------------+
>
>-- End of excerpt from Tom Sundius U of Helsinki +358 0 1918339