[molpro-user] Making SCF converge to the ground state

[Kirk Peterson]

Terry,

since you mention the CAS works ok, have you tried using those  
orbitals as the starting guess to
the HF program?

-Kirk

On May 15, 2007, at 12:00 PM, Terry Frankcombe wrote:

>
> Hi folks
>
> I've been running into a problem with my HF orbital occupations  
> quite a
> lot recently.  I'm trying to do calculations on a triplet system, but
> the SCF program insists on converging to a state that isn't the ground
> state.
>
> The problem is illustrated by the following output from a dump to a
> molden file:
>
>  DUMP ORBITAL  1.1 AS ORBITAL    1  occ=    2.0000  eig=  -15.6686
> GROUP=   2
>  DUMP ORBITAL  2.1 AS ORBITAL    2  occ=    2.0000  eig=  -15.6633
> GROUP=   2
>  DUMP ORBITAL  3.1 AS ORBITAL    3  occ=    2.0000  eig=  -11.3487
> GROUP=   2
>  DUMP ORBITAL  4.1 AS ORBITAL    4  occ=    2.0000  eig=   -1.2977
> GROUP=   2
>  DUMP ORBITAL  5.1 AS ORBITAL    5  occ=    2.0000  eig=   -0.9600
> GROUP=   2
>  DUMP ORBITAL  6.1 AS ORBITAL    6  occ=    2.0000  eig=   -0.6882
> GROUP=   2
>  DUMP ORBITAL  7.1 AS ORBITAL    7  occ=    2.0000  eig=   -0.5551
> GROUP=   2
>  DUMP ORBITAL  8.1 AS ORBITAL    8  occ=    2.0000  eig=   -0.5302
> GROUP=   2
>  DUMP ORBITAL  1.2 AS ORBITAL    9  occ=    2.0000  eig=   -0.4495
> GROUP=   2
>  DUMP ORBITAL  2.2 AS ORBITAL   10  occ=    1.0000  eig=   -0.6223
> GROUP=   1
>  DUMP ORBITAL  9.1 AS ORBITAL   11  occ=    1.0000  eig=   -0.5463
> GROUP=   1
>
> The energy of the singly occupied orbital 2.2 is lower than the doubly
> occupied orbitals 7.1, 8.1 and 1.2!  The chemistry agrees that this is
> wrong and that the second unpaired spin should be orbital 1.2, mostly
> localised to the same atom as 9.1 (on an incoming nitrogen atom).  The
> calculated SCF energy is about 0.3 hartree higher than it should be.
> CASSCF calculations give the correct state and energy, with the second
> electron "excited" out of that 1.2 orbital.
>
> I've played quite a bit with orbital shifts and the initial guess,  
> to no
> avail.  How can I convince Molpro that a singly occupied orbital  
> deep in
> the spectrum is wrong?
>
> Regards
> Terry
>
> -- 
> Dr Terry Frankcombe
> Physical Chemistry, Department of Chemistry
> Göteborgs Universitet
> SE-412 96 Göteborg Sweden
> Ph: +46 76 224 0887   Skype: terry.frankcombe
> <terry at chem.gu.se>
>
>