# [molpro-user] Calculating molecular oxygen excited state

Jacky LIEVIN jlievin at ulb.ac.be
Fri Sep 25 08:23:10 BST 2009

```Dear Lorenzo,

Please find below a modified version of your input. The results are
looking fine:

(CASSCF(1)-GROUND(2))*219474.631      =      7729.42504739  AU
(CASSCF(2)-GROUND(2))*219474.631      =     11956.61935055  AU
(CASSCF(3)-GROUND(2))*219474.631      =      7729.42504740  AU
(MRCI(1)-GROUND(3))*219474.631        =      7741.10269691  AU
(MRCI(2)-GROUND(3))*219474.631        =     12896.24859442  AU

Modifications are:
1) the use of state averaged MCSCF
First for ensuring the degeneracy of the delta state (one component of
symmetry 1 and one of symmetry 4): group theory tells us that deltag
correlates to Ag + B1g in D2h symmetry
Second for describing the second state (sigma + g) of symmetry 1:
sigma + g correlates to Ag
Both electronic states must thus be calculated in a single MCSCF state
averaged calculation defined by 2 WF directives.
Note the lquant directive given on each WF line and for each
calculated state
Note the degeneracy CASSCF(1)=CASSCF(2)= energy of delta state

2) calculate the two low-lyng states of symmetry 1 in the same MRCI
calculation: MRCI(1) gives the delta state and MRCI(2) the sigma state

best wishes

Jacky

-------------------------------------------------------------------------------

***,test
basis=aug-cc-pVTZ
r = 2.3
geometry={O1; O2,O1,r}

!------- Ground
{RHF; WF, NELEC=16, SYMMETRY=4, SPIN=2; CLOSED,
3,1,1,0,2,0,0,0;OPEN, 1.6,1.7}
Ground(1)=energy

{MCSCF}
Ground(2)=energy

{MRCI}
Ground(3)=energy

!------- First
and Second excited state
{RHF; WF, NELEC=16, SYMMETRY=1, SPIN=0; OCC, 3,1,1,0,2,1,0,0;}
excited(1)=energy

{MCSCF;
WF, NELEC=16, SYMMETRY=1, SPIN=0;state,2;lquant,2,0
WF, NELEC=16, SYMMETRY=1, SPIN=0;state,1;lquant,2}
casscf(1)=energy(1)
casscf(2)=energy(2)
casscf(3)=energy(3)

{MRCI; WF, NELEC=16, SYMMETRY=1, SPIN=0;state,2}
mrci(1)=energy(1)
mrci(2)=energy(2)

show (Excited(1)-Ground(1))*219474.631
show (casscf(1)-Ground(2))*219474.631
show (casscf(2)-Ground(2))*219474.631
show (casscf(3)-Ground(2))*219474.631
show (mrci(1)-Ground(3))*219474.631
show (mrci(2)-Ground(3))*219474.631
---

Le 24 sept. 09 à 17:12, Lorenzo Lodi a écrit :

> basis=aug-cc-pVTZ
> r = 2.3
> geometry={O1; O2,O1,r}
>
> !------- Ground state, triplet sigma gerade minus
> {RHF; WF, NELEC=16, SYMMETRY=4, SPIN=2; CLOSED,
> 3,1,1,0,2,0,0,0;OPEN, 1.6,1.7}
> Ground(1)=energy
>
> {MCSCF}
> Ground(2)=energy
>
> {MRCI}
> Ground(3)=energy
>
> !------- Second excited state, singlet sigma gerade plus
> {RHF; WF, NELEC=16, SYMMETRY=1, SPIN=0; OCC, 3,1,1,0,2,1,0,0;}
> Excited(1)=energy
>
> {MCSCF; LQUANT,0; WF, NELEC=16, SYMMETRY=1, SPIN=0}
> Excited(2)=energy
>
> {MRCI; WF, NELEC=16, SYMMETRY=1, SPIN=0}
> Excited(3)=energy
>
> show (Excited(1)-Ground(1))*219474.631
> show (Excited(2)-Ground(2))*219474.631
> show (Excited(3)-Ground(3))*219474.631
> ---

_____________________________________
Jacky Liévin
Service de Chimie Quantique et Photophysique
Université Libre de Bruxelles, CPi 160/09
50 av F.D. Roosevelt
B-1050 Bruxelles
Belgium
Tel: +32-2-650 4089
Fax: +32-2-650 4232
_____________________________________

```