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

[H.-J. Werner]

Hi,
by default Molpro freezes the occupations after a certain number of iterations, 
and if at this stage the occuation happens to be wrong it will converge to
the excited state. This can be controlled by the parameter NITORD.
Try, e.g.,  rhf,nitord=50!

Note: 
(i) don't confuse NITORD (refers to "order" with parameter NITORT (refers to "orthogonalization")
(ii) Note that in a restart from previous orbitals the occupations are frozen from
the beginning unless NITORD is specified. It should also be possible to
use rotate,1.2,2.2 in a second rhf calculation.

If nothing helps, please send the input and I'll take a look!
Best regards
Joachim Werner


On Di, 15 Mai 2007, 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>
>

-- 
Prof. Hans-Joachim Werner
Institute for Theoretical Chemistry
University of Stuttgart
Pfaffenwaldring 55
D-70569 Stuttgart, Germany
Tel.: (0049) 711 / 685 64400
Fax.: (0049) 711 / 685 64442
e-mail: werner at theochem.uni-stuttgart.de