EXPBAS desymmetryzation


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Posted by Lukas F. Pasteka on July 26, 2011 at 11:57:08:

Hello,

I have troubles converging CASSCF without symmetry (oscillatory behavior with no help from level shifting or turning off the quasi newton), while the computation with symmetry on converges smoothly.

I would like to use the orbitals from symmetric computation as a start for the one with no symmetry.

How would I do that properly?

I tried this:
1) run gateway/seward -> scf -> casscf with symmetry on
2) copy rasorb to inporb and runfile to runfil1
3) execute expbas with the noexpand and dessymetrize keywords
4) copy the desymorb to inporb
5) run gateway/seward with symmetry off
6) run casscf with the lumorb command

No matter how I modify the input, the energy of the second casscf differs from the first one, even though the active space size, spin and root are equivalent.

I would understand the second casscf converging to the different energy, but it differs from the first iteration, even if I use the cionly keyword.

Does it have something to do with ordering of atoms in gateway/seward or orbitals in casscf?

Thank you for any help.

Lukas


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