[molpro-user] Difference in optg and optg+freq outputs

Marco Verdicchio m.verdicchio at gmail.com
Mon Mar 5 10:55:47 GMT 2012

Dear all,

i'm trying to perform a optg+frequencies calculation on a small molecule at
the caspt2 level of theory.
I made first a simple optimization and then, in the same input (same
geometry, same starting orbitals...exactly the same input!) i put only the
two strings:


and i repeat the calculation.
The strange thing i found is that despite the two inputs are exactly the
same (except for the freq command) the optimizations fall in two different
minima (with an energy difference of 0.0001 hartree and little difference
in structural parameters...)

Can someone explain me how the request for a frequencies analysis can
change also the optimization steps that come before?!
Thank you very much for any help.

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