

> 
> Dear netters,
> 
> we have the following problem with GAMESS (US):
> 
> While calculating the molecule:
> 
> 
    It means the initial geometry is too bad to optimize. Particulary
you should be careful about bond length. In this case, I found the Si-Cl
bond lengths are too short. It's standard length is somewhere around
2.1 angstrom. So, the following input will work.

$data
1,1-dimethyltetrachlorodisilane
c1
Si
Si 1  2.4
C  1  1.88  2 110.0
C  2  1.88  1 110.0  3  180.0
Cl 1  2.1   2 110.0  3  120.0
Cl 1  2.1   2 110.0  3 -120.0
Cl 2  2.1   1 110.0  4  120.0
Cl 2  2.1   1 110.0  4 -120.0
H  3  1.1   1 110.0  2  180.0
H  3  1.1   1 110.0  9  120.0
H  3  1.1   1 110.0  9 -120.0
H  4  1.1   2 110.0  1  180.0
H  4  1.1   2 110.0 12  120.0
H  4  1.1   2 110.0 12 -120.0
 $end

Of course you need to put COORD=ZMT in $contrl group and I think use
NZVAR=36 is a good idea. Also if you are seeking global minimum,
starting another optimization with torsion of C-Si-Si-C set 60 is
necessary.

Hideaki Shimizu