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Problem fixing torsional angle in during geometry optimization with SA-CASSCF

Rami
rami.gherib@mail.utoronto.ca


Hello,

I am trying to perform a geometry optimization while constraining one of the torsional angles in my molecular system. I'm using state-averaged CASSCF and I would like to optimize on the ground state potential energy surface. The problem I am facing is that during the optimization, the torsional angle that is intended to be fixed, changes significantly (from 110 to 128.6 degrees). I using the following commands to fix the desired torsional angle:

nzvar=1 ! in  $CONTRL

and

$ZMAT DLC=.T. AUTO=.T. nonvdw(1)=1,26
IFZMAT(1)=3,3,4,14,17
$end

I would also like to mention that I used the same set of commands to optimize the same molecule at a different fixed angle on the excited state surface. The latter did not have this problem. The input and output files are attached.

Thank you,

Rami

This message contains the 6603 kb attachment
[ v90copt.out ] output file

[ This message was edited on Fri May 18 '18 at 10:18pm by the author ]


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