Author Topic: Geometry optimization of the lowest triplet state  (Read 324 times)

lasermichel

  • Newbie
  • *
  • Posts: 9
  • Karma: +0/-0
    • Working group for high resolution spectroscopy
Geometry optimization of the lowest triplet state
« on: April 20, 2018, 01:19:24 pm »
Hi,

I'm trying to optimize the lowest triplet state of 3-cyanoindole using CC2 (using spin component scaling) with the cc-pVTZ basis set. Control file reads:

$ricc2
  cc2
  geoopt model=cc2       state=(a{3} 1)
  scs   cos= 1.20000   css= 0.33333
$response
operators=diplen,qudlen
$excitations
irrep=a multiplicity=3 nexc=2
preopt=4
thrdiis=3

There is an error in the gradient step: cc_parse_states> inconsistency in state input!

Also the energies of the lowest two triplets, which are given in the first run of ricc2 are both negative! What is going wrong here?

Connected to that problem: What I'm really interested in, ist the optimization of the second excited singlet state. While the first excited singlet was no problem, I always run into a conical intersection with the first state, when trying to optimize the second one. For other indoles I have a good guess about the structure of the second state, so that I can avoid the crossing by choosing a good starting geometry. This does not work here. A colleague gave me the advice that the structure of this second singlet state should be similar to that of the lowest triplet. Therefore I try to optimize the tríplet for a better idea about the second singlet structure. Any other ideas, of how to avoid running into the CI?

Thanks, Michael