Issue with CCSD(T)-F12 Calculation – RHF Not Converged

[Mounsif ABBES]

Hi Molpro Community,

I am running a CCSD(T)-F12 calculation, but I encounter the following error:
 ?Error: RHF not converged. This error exit can be avoided using the IGNORE_ERROR option on the ORBITAL directive

I have tried starting with a smaller basis set and gradually increasing it, but the problem persists.

Please find my input file below. Any guidance on resolving this issue would be greatly appreciated.

Thank you in advance!
Mounsif ABBES


*** Title
memory,1200,m
geomtyp=xyz
geometry={
16

 C                  2.60385100   -0.94205800   -0.14175400
 H                  2.46708400   -1.67982200    0.64842000
 H                  2.46558600   -1.44705500   -1.09726900
 H                  3.61407600   -0.54444900   -0.09296200
 C                  1.61700800    0.17777800    0.01125000
 C                  1.90239900    1.46193300    0.20225600
 H                  1.15939300    2.23887000    0.31859700
 H                  2.93581400    1.77731400    0.27114500
 C                  0.19812300   -0.26922200    0.00791000
 C                 -0.96642700    0.94395900   -0.05727800
 H                 -1.02302300    1.24905400    0.99097700
 H                 -0.62501700    1.69932500   -0.75756900
 O                 -2.10912400    0.43021800   -0.53763200
 O                 -2.65197800   -0.39889700    0.42025600
 H                 -3.36863400   -0.83813000   -0.07135700
 O                 -0.20827300   -1.36750100    0.07434100
}


charge=1
spin=1
hf

BASIS=avdz

ccsd(t)-f12b

---

[Peter Knowles]

There are two things that you can do to make this job run better.

1. Do Hartree-Fock for the closed-shell neutral first, to provide a better guess for the open-shell calculation

2. If you change the basis to avdz, it makes no sense to immediately do a ccsd(t)-f12 calculation - you should get the Hartree-Fock orbitals in this basis first.

So something like

BASIS=avdz

hf

charge=1

spin=1

hf

ccsd(t)-f12b

You probably also know that normally at least triple-zeta basis sets should be used for correlation calculations, even with F12.

Peter

On 8 Dec 2025, at 13:50, Mounsif ABBES <monc...@gmail.com> wrote:

External email to Cardiff University - Take care when replying/opening attachments or links.

Nid ebost mewnol o Brifysgol Caerdydd yw hwn - Cymerwch ofal wrth ateb/agor atodiadau neu ddolenni.

--
You received this message because you are subscribed to the Google Groups "molpro-user" group.
To unsubscribe from this group and stop receiving emails from it, send an email to molpro-user...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/molpro-user/dbdfb872-fe79-423b-9fd0-678fe4fdbf3cn%40googlegroups.com.

[Mounsif ABBES]

That worked. Thanks a lot.

Best Regards,
Mounsif ABBES