Calculating Excited State's Energy for Potential Energy Surface

[Deniz Kahraman]

Dear DIRAC users,

I am trying to calculate the potential energy surface of BiC diatomic species along bond length and thus trying to understand the optimized bond length and vibrational frequency. I have succeeded for Anion and Neutral but when I tried to calculate the neutral's first excited state by using previously calculated DFPCMO and .REORDER (doubly occupied HOMO and singly occupied HOMO-1) I was not sure if I am doing it correctly. I have used the input below to change the order of HOMO and HOMO-1 in the neutral. Is it a good way to calculate the potential energy surface of the excited state? Am I missing something? Are there any other alternatives to understand the optimized bond length of an excited state and to calculate its frequency in DIRAC? Also, if this is correct, how should I reorder for the second excited state (meaning singly occupied HOMO-2) should it be 1..42,44,45,43 or something else? Thanks a lot for your help!

My Input: 

**DIRAC
.WAVE FUNCTION
**GENERAL
.PCMOUT
**WAVE FUNCTION
.REORDER MO
1..43,45,44
.SCF
*SCF
.MAXITR
999
.CLOSED SHELL
88
.OPEN SHELL
1
1/2
**MOLECULE
*CHARGE
.CHARGE
 0
*BASIS
.DEFAULT
dyall.acv3z
**HAMILTONIAN
.DFT
PBE0
*DFT
.SAOP
LB94
**END OF

Best wishes!

Deniz