[molpro-user] Why SCF results do not give the lowest energy?

[cjrosa at ualg.pt]

I want to calculate the SCF energy of H2O triplet in geometry close to  
the C2V symmetry. For this  geometry that I study the state of lower  
energy is the 3B1 followed by 3B2 and 3A2 respectively. I have no  
problem in calculate each one of these energies. For this calculation  
I use the follow input:

***,h2o

BASIS=aug-cc-pvqz

R=7.0
RHH=1.402
RH=(RHH/2.0)*toang
ROHH=R*toang

geomtyp=xyz
geometry={
3
Cartesian coordinates of each atom
O1,0.0000000000, ROHH*cos(90.0)     ,  ROHH*sin(90.0)
H1,0.0000000000,-RH                 , 0.000000000
H2,0.0000000000, RH                 , 0.000000000
}

{RHF;
WF,10,?,2;                           !? can be 2 for B1, 3 for B2 or 4 for A2
}
---

The problem occurs when I use lower symmetry to study the system.
If I use Cs symmetry and I ask for the lower A?? energy I get the 3A2  
energy instead of 3B1 energy. (That is, I get the second energy of  
state A??!!!) . The unique difference in the input is:

...
geometry={
X;
3
Cartesian coordinates of each atom
O1,0.0000000000, ROHH*cos(90.0)    , ROHH*sin(90.0)
H1,0.0000000000,-RH                ,0.0000000000
H2,0.0000000000, RH                , 0.000000000
}
...
{RHF;
WF,10,2,2                              !or WF,10,1,2 for the A? state
}
---

In the same way, if I use C1 symmetry I get the 3A2 energy (the third  
energy!!!). The unique difference in the input is:
...
geometry={
NOSYM;
3
Cartesian coordinates of each atom
O1,0.0000000000, ROHH*cos(90.0)    , ROHH*sin(90.0)
H1,0.0000000000,-RH                ,0.0000000000
H2,0.0000000000, RH                , 0.000000000
}
...
{RHF;
WF,10,1,2
}
---
That is, if I use lower symmetry I never get the 3B1 energy
Could anyone explain me why it happens. Thank you.



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