thank you for time and answer.
>>Q1: Is there any difference between kstate(1)=1,1,1,0,1 and
>kstae(1)=1,1,1,1,0 for XMCQDPT. Since Heff has the same size, i am a
>little bit confused, especially after reading of the manual from
>GAMESS-US. I don't understand how can we use correctly kstate array,
>while situation with nstate absolutely clear (nstate == Heff)
>As to the question on differences between kstate(1)=1,1,1,0,1 and
>kstae(1)=1,1,1,1,0 runs, they do differ. In the first case,
>the model space is formed by the first, second, third, and fifth
>CASCI root. The fourth CASCI state is computed at the very early
>stage of the run and only because it is required by Davidson
>diagonalization procedure to compute the fifth state. After this,
>the fourth state is discarded and CASCI states are renumbered to
>condense their labels. This means that the fifth CASCI state is
>referred to as the CASCI state #4 throughout the rest of computations.
ok, it sounds very interesting. So, if an order of states from CAS-CI part is 1,1,1,0,1 we can setup kstate(1)=1,1,1,0,1 and basically remove "undesired" state from PT2 part. Does it make sense? Is this equivalent to setting of the AVECOE and WSTATE (XMCQDPT) arrays to be AVECOE(1)=1,1,1,0,1 and WSTATE(1)=1,1,1,0,1. If not, what is the best strategy, to use kstate or avecoe/wstate? Or, maybe, we can just use nstate/wstate/avecoe combination and forget about kstate.
>>Q2: Is there any correlation between nstate (SA-CASSCF) and Hef.
>Thus, if Heff <= nstate then no problem at all. But if Heff > nstate
>i am confused about eigenvalues of Hef and nature of "extra" states
>from CAS-CI side. Could you give, please, some advice if any, about
>correlation between nstate (CAS-CI) and Heff.
>The states used in XMCQDPT2 and MCQDPT2 are just the CASCI states
>computed with the (canonicalized) orbitals generated by the
>preceeding CASSCF or SA-CASSCF computations. For instance,
>one can use SA2-CASSCF to generate orbitals, then use 10 states to
>construct Heff. The first two CASCI states will be those of SA2-CASSCF
>roots, the extra states will be just the additional eigenvectors of
What if those additional eigenvectors contribute to some low lying states? Do we need repeat CASSCF part once again and include those extra states?
>>Q3: Is it good idea to do SA-CASSCF/XMCQDPT via singlets and triplets
>simultaneously in case of high spin-orbit coupling. Actually, i am
>going to check singlets only and singlets-triplets, but maybe it make
>I'd suggest you to use to use SA-CASSCF averaged over both singlet
>and triplet states to generate the same set of MOs to be used in PT2
>computations. Firefly v. 8.0.0 has some new features specifically
>tailored for these types of jobs which I'll describe in my next post
>to this thread.