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Re^3: Problem with SOC (spin-orbit coupling) calculations

Alex Granovsky

Dear Maksim,

The problem you encountered is caused by invalid transt, cidrt1
and cidrt2 groups. For your computations these groups should be
as follows:

 $cidrt1 fors=.true. nfzc=8 ndoc=0 nval=9 next=0 naos=1 nbos=1 nalp=1 $end

 $cidrt2 fors=.true. nfzc=8 ndoc=0 nval=9 next=0 naos=0 nbos=0 nalp=3 $end

  numci=2 numvec=1 nfzc=8 nocc=20 iroots(1)=11,11

Some additional comments:

1. Do not use coord=zmt or zmtmpc for runs exporting/importing orbitals,
as molecule could be rotated differently as in the preceding run.
Use coord=unique instead. In addition, you may need to recompute
orbitals from the scratch.

2. Use $contrl wide=.t. $end throughout to export/import orbitals.

Kind regards,
Alex Granovsky

On Fri Jan 15 '16 11:58am, Maksim Shundalau wrote
>Dear Alex!

>Firstly I calculated terms of the YbCs molecule at the SA-CASSCF level of theory from asymptotical limit (20 A) to the shot distance (3 A) point-by-point with step 0.05 A. I get 3 valence electrons and 12 orbitals for active space, and 14 states (11 doublets and 3 quartets) in SA procedure. I use Stuttgart ECP basis sets. I perform single-point calculation at a certain point, and then I take optimized vectors from PUNCH and perform single-point calculation at a next point, etc. Also I’m watching the states in SA.
>In result I have smooth PECs for the ground and some excited states of YbCs.
>For example, for the ground state PEC I have:

>7.65 A CAS=-52.5164130391
>7.70 A CAS=-52.5163908210
>7.75 A CAS=-52.5163695661
>7.80 A CAS=-52.5163495738

>Secondly I calculated the terms at the XMCQDPT2 level of theory, and again I have smooth PECs. The details of the XMCQDPT2 calculations I can also describe, but the SOC calculations are performed on the CAS-vectors.

>At least I calculated SOC with optimized CAS-vectors, and I have a problem. I get “breaks” in PECs, for example:

>7.65 A CAS+SOC=-52.5164465294
>7.70 A CAS+SOC=-52.5164233281
>deltaE=0.00000115 !!!!!!!!!!!!!!!!!!
>7.75 A CAS+SOC=-52.5164221806
>7.80 A CAS+SOC=-52.5163986729
>Thank you very much,
>With best regards,
>Maksim Shundalau.
>On Thu Jan 14 '16 4:16pm, Alex Granovsky wrote
>>Dear Maksim,

>>could you please describe in details your computational protocol?

>>Kind regards,
>>Alex Granovsky
>>On Tue Jan 12 '16 12:16pm, Maksim Shundalau wrote
>>>Dear Alex!

>>>I’ m trying to calculate PECs of the YbCs molecule at the CAS(3,12)/XMCQDPT2 + SOC (spin-orbit coupling) level of theory with Stuttgart ECP basis sets.
>>>I have smooth terms at the CAS(3,12) and at the XMCQDPT2 levels of theory. But I have “breaks” in PECs, when I’m calculating SOC (see, for example, figs.pdf).

>>>What’s the problem here?

>>>Thank you very much,
>>>With best regards,
>>>Maksim Shundalau.

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