*From*: "Stefan Beyreuther" <stefan #*at*# indi.aci.uni-heidelberg.de>*Subject*: SUMMARY: Wilson Out-Of-Plane Coordinate*Date*: Fri, 20 Sep 1996 00:50:30 -0600

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