[molpro-user] No convergence in Boys Localization after 200 iterations

[Muammar El Khatib]

Dear *.*,


I'm trying to do orbital localization in a conjugated molecule using the Boys
method. In my calculation, I turned off the symmetry by specifying so using the
NOSYM keyword as suggested in § 32.9.2 in the manual. I also used the NOORIENT
option in the geometry block. When reading, I found that a poor localization is
likely to happen when you have a strongly conjugated system (§ 32.9.4) which is
my case.

So I proceed as follows: I do my HF calculation, and then the localization.

Below, I'm pasting a relevant part of this calculation:


-----------------------8<-----------------8<-----------------------------------

:***,p_2
memory,240,m;

file,1,p_2.int,new;
file,2,p_2.orb,new;

gprint,basis;
gprint,orbital;


symmetry,nosym;

geometry={
MY GEOMETRY
}


basis=cc-pvdz

int;

! HF
{rhf-scf;
wf,172,1,0;
!       0  0  0  0  0  0  0  0
orbprint,4;
}

put,molden,p_2.molden;


{locali;
save,2103.2;
core,26;
group,65.1,68.1,71.1,77.1,-86.1;
group,27.1,-64.1,66.1,67.1,69.1,70.1,72.1,-76.1;
print,centers;
}

put,molden,p_2sep.local;
-----------------------8<-----------------8<-----------------------------------

The output prints the following message:

?NO CONVERGENCE IN BOYS LOCALIZATION AFTER 200 ITERATIONS. SYMMETRY= 1  DR= 0.4497D-08

In spite of the convergence problem, MOLPRO gives me a set of localized orbitals
that, as said in the manual, are poorly localized (no convergence in the
process).

What would you suggest me to try?. I checked if there existed some card to
change the number of iterations, but I think that if in 200 it didn't do it so
it's not a good idea to increase it. Then, there is the option of localization
thresholds but I'm not sure that it'll make the localization to converge or what
values are sensibles to do it.


I'd be glad if someone could help me.


Regards,

PS. I tried using the Pipek-Mezey criterion and the calculation converged, but
I'm interested to know how to troubleshoot this problem in Boys. This is
because, even the Boys localization didn't converge, the orbitals seem better
localized.

--
Muammar El Khatib.
Linux user: 403107.
GPG Key = 127029F1.
http://muammar.me | http://proyectociencia.org
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