Author Topic: converged problems for open-shell system using BP86  (Read 4296 times)

greisen

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converged problems for open-shell system using BP86
« on: January 10, 2011, 06:34:21 pm »
Hi all,

I am optimizing a cluster of ions where I have first optimized using the highest spin state. After convergence I took those coordinates and transfered them into a new coordinate file. I then used a lower spin state but now I get problems with the scf convergence of the my cluster. I have used default settings for the scf-options and I am using RI in order to speed up calculation. Any flags to set that might help convergence of the cluster?

Thanks in advance

antti_karttunen

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Re: converged problems for open-shell system using BP86
« Reply #1 on: January 12, 2011, 10:05:51 am »
Hi,

Try changing the following keywords (see the manual for details):
  $scfdamp start=4.000 step=0.100 min=0.500
  $scforbitalshift closedshell=.4
  $scfiterlimit 150

If this does not help, just increase the damping (and perhaps the shift, too):
  $scfdamp start=8.500 step=0.200 min=0.500
  $scforbitalshift closedshell=.5
  $scfiterlimit 200

For closed-shell systems, use automatic $scforbitalshift instead of closedshell.

These keywords are usually the most straightforward way of reaching convergence. Fermi-smearing can also be very helpful, especially when used with the "nue" option (see manual for $fermi)

Regards,
Antti
« Last Edit: January 12, 2011, 10:07:34 am by antti_karttunen »

amavr78

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Re: converged problems for open-shell system using BP86
« Reply #2 on: January 12, 2011, 02:36:04 pm »
In some cases, it may help convergence for low-spin, if you use the preconverged high-spin orbitals.