Subject: linear molecule optimization

From: "Emadeddin Tajkhorshid" <[email-masked]>
Date: Sun, 12 Jul 1998 20:07:16 -0700

Dear colleagues

Locating a transition state, I have to optimize a molecule in a linear
conformation. I tried to use redundant coordinate as well as cartesian
coordinnates to optimize the system. However, always the job (G94) stops
because of the very large RMS in the change in the internal coordinates during
the geometry optimization. I decided to first look at another (standard) linear
molecule, namely allene molecule (H2C=C=CH2). G94 automatically assigns the
following bond angles by calling them "L" and proceeds successfully to optimize
the system.

 ! A4    L(1,2,5)              180.             estimate D2E/DX2             !
 ! A5    L(1,2,5)              180.             estimate D2E/DX2             !

First of all, I would like to know whether it is possible to define such
coordinates in the input file.

And ...

My main problem is to optimize the linear system. Any comment and/or suggestion
with regard to the linear system optimization is highly appreciated.

Thanx in advance

-- 
Emad
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E. Tajkhorshid				
German Cancer Research Center; DKFZ             Tel: +49 6221 42 2340
Dept. Molecular Biophysics (H0200)              FAX: +49 6221 42 2333
P.O.Box 101949			   
69009 Heidelberg, Germany     Email: [email-masked] 
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* "Never express yourself more clearly than you think." -Niels Bohr *
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