[molpro-user] Localized orbitals as starting guess for CASPT2

Marco Verdicchio m.verdicchio at gmail.com
Tue Feb 14 10:52:48 GMT 2012

Dear all,

i'm trying to do an CASPT2 calculation on a simple molecule by using
localized orbitals as starting guess for the CAS active space.
In particular, since i want to choose the orbitals to correlate, i first
make a localization and then i exchange the orbitals in order to include
the choosen ones in the active space. Here below some line from my input:

{rhf; wf,33,1,1;}  ! hf calculation

{locali,pipek; noorder;} ! localization

{multi; closed,15; occ,19;    ! casscf(3,4)
 start,2100.2; rotate,14.1,16.1,0;}

{rs2;                 ! caspt2



This example is for a (3,4) active space where i want to include the single
occupied orbital (17.1) and the internal (14.1) which i exchange with the
(16.1) in order to inclued its in the active space. Obiviously i had
already plotted the localized orbital in a separate calculation and choose
the orbital 14 for its chemical relevance. The record 2100.2 is where the
program put the localized orbitals (i can't change it since if a i put a
save card after the locali command i get an error!!).

My questions are: is this input right for my purpouse!? I'm a little bit
confusing since if i plot the orbitals that are in the molden file i found
that the 16.1 is totally different from the orbital i choose (ok that's are
Natural Orbitals, but are so differents!?)...why the multi calculation
should change the order of the orbital between active and inactive?!!? and
how i can get sure that the orbitals in the active space are the onces i

I hope i was clear enough...
Thank you in advance for any help you could give me.

Best regards,

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