# [molpro-user] RSPT2 for an open-shell degenerate state

Victor G. Solomonik sol at isuct.ru
Fri Apr 23 20:00:08 BST 2010

```Dear Wenli,

thanks a lot for your note. However, an independent RS2 treatment of the
Ni^3+ 4F state still yields a broken degeneracy of this state (see
below). An independent calculation of each state in 4,6,7 symmetries
(by setting STATE,1,istate) yields a broken degeneracy anyway.

If you are lucky to get degenerate RS2 energies of 4F state, would you
let me know the input which yields degenerate energies?

Best regards,
Victor

P.S. I would highly appreciate receiving comments from the members of
molpro community and the molpro developers.

************************************************************
PROGRAM SYSTEM MOLPRO, Version 2009.1, Patch level 20
***,Ni^3+ cc-pwCVTZ-DK 4F state
memory,200,M
gprint,orbitals=10
dkroll=1
geometry={NI}
basis={spdfg,NI,WCVTZ-DK;c}
{rhf,MAXIT=250;WF,30,1,0}
{multi
config;
wf,25,1,3;
wf,25,4,3;state,3;
wf,25,6,3;state,3;
wf,25,7,3;state,3;
canonical,ci;
}

{rs2,
core,2,1,1,0,1,0,0,0
wf,25,1,3
state,1
}
!RSPT2 STATE 1.1 Energy            -1517.659070068412
{rs2,
core,2,1,1,0,1,0,0,0
wf,25,4,3
state,2
}
!RSPT2 STATE 1.4 Energy            -1517.667517003226
!RSPT2 STATE 2.4 Energy            -1517.665142241958
{rs2,
core,2,1,1,0,1,0,0,0
wf,25,6,3
state,2
}
!RSPT2 STATE 1.6 Energy            -1517.666295721542
!RSPT2 STATE 2.6 Energy            -1517.666400254651
{rs2,
core,2,1,1,0,1,0,0,0
wf,25,7,3
state,2
}
!RSPT2 STATE 1.7 Energy            -1517.666653620887
!RSPT2 STATE 2.7 Energy            -1517.666039975024
********************************************************

> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> From:        Zork Zou <zorkzou at yahoo.com.cn>
> Date:        April 21, 2010, 2:26:52
> Subject:     [molpro-user] RSPT2 for an open-shell degenerate state
> --====----====----====----====----====----====----====----====----====----===--
> Dear Victor,
>
> In your RSPT2 calculation the degeneracy in the 4F state is broken
> because you use different CASPT2 methods. For the state 1.1, it is
> single-root  CASPT2 method; whereas for the states 1.4~3.4, 1.6~3.6,
> and 1.7~3.7, the method is multi-root CASPT2 in which both 4F and
> 4P are calculated.
>
> To get degenerate energies, please calculate 4F and 4P states
> separately in RS2  by setting STATE. The same is also true for MRCI.
>
> Best wishes,
> Wenli
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

```

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