# [molpro-user] caspt2 in ion molecule complexes

KhanBasir Ahamed (자연과학부) bakhan at unist.ac.kr
Wed Sep 6 04:58:24 CEST 2017

```Dear Molpro users,

I  would like to calculate the first five potential energy curves (singlet or triplet,may be)

of benzene-proton complexes by CASPT2 method. My question is that can I calculate

the singlet and triplet states simultaneously of this system? I put my input file below for

singlet for three states only :

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

basis=6-311++g(d,p)

ANGSTROM

geometry={
X
H, 1, B1
C, 1, B2, 2, T1
C, 1, B2, 2, T1, 3, D1
C, 3, B3, 1, T2, 2, -D2
C, 3, B3, 1, T2, 2, D2
C, 4, B3, 1, T2, 2, D2
C, 4, B3, 1, T2, 2, -D2
H, 3, B4, 1, T3, 2, D3
H, 4, B4, 1, T3, 2, D3
H, 5, B5, 7, T4, 4, -D4
H, 6, B5, 8, T4, 4, D4
H, 7, B5, 5, T4, 3, D4
H, 8, B5, 6, T4, 3, -D4
}

B1=1.5
B2=1.417492
B3=1.382571
B4=1.098639
B5=1.081809
T1=90.0
T2=59.547
T3=179.778
T4=118.806
D1=180.0
D2=90.0
D3=180.0
D4=180.291

set,nelec=42
hf

{casscf
occ,8,7,6,4
closed,7,5,4,2
natorb,,ci
wf,42,1,0;state,3
wf,42,2,0;state,2
}
{rs2c,shift=0.5
occ,8,7,6,4
closed,7,5,4,2
natorb,,ci
state,1,1
wf,42,1,0
}
{rs2c,shift=0.5
occ,8,7,6,4
closed,7,5,4,2
natorb,,ci
state,1,2
wf,42,1,0
}
{rs2c,shift=0.5
occ,8,7,6,4
closed,7,5,4,2
natorb,,ci
state,1,1
wf,42,2,0
}
----------------------

How can I calculate a few lower energy triplet states in my system.

Is there any way to know, in case of triplet, a state of a

particular symmetry is the lowest energy triplet states?

I will be glad if anyone can help for the problem.

Best regards.

Basir Ahamed Khan

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