Subject: geom optimization

From: Chun Chung Chan <[email-masked]>
Date: Thu, 23 Nov 2000 16:05:52 +0100 (MEZ)

Dear all,

We are currently working on the geometry optimization of a linear chain
molecule Se5Br2 under the following conditions:

G98, Rev A.6
B3LYP/6-311G
opt

The optimized structure takes a planar zigzag form. The bond angles range
>from 93 to 96 degrees and the bond lengths of Se-Br and Se-Se are 2.45 and
2.52 angstroms, respectively. The structure looks reasonable to me and the
four optimization criteria in G98 are fulfilled. However, the freq
calculation shows that there are four imaginary freqs ranging from -24 to
-61 cm**-1. We repeat the calculation by "opt=(calcfc,tight)" but still
get more or less the same imaginary freqs. Other than trying different
input structures, could any one of you please give us some hints how to
get the truely optimized ground state structure. 

Many thanks,
Jerry

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* Jerry Chun Chung CHAN                     [email-masked] *
* Universitaet Muenster	                                         *
* Institut fuer Physikalische Chemie    fax:   0049-251-83-29159 *
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