Article ID: 1055 - Last Modified: June 2, 2011
What do I do if the SCF won't converge in Jaguar?
If you are having difficulty getting SCF to converge, add the keyword iacc=1 to the gen section of your input file. This keyword setting increases the accuracy by using larger pseudospectral grids.
If the energy jumps around during the SCF, it may be that the orbital occupations are switching between two electronic states. To prevent this, you can shift the virtual orbitals up in energy by setting vshift=1.0 (you may need to use a larger value). This typically slows the rate of convergence, so you should increase the limit on the number of SCF cycles by setting maxit=150. The use of vshift can be especially useful for organometallics.
A good alternative SCF convergence algorithm can be employed by setting iconv=4.
You can also try obtaining convergence with a smaller basis set, then using the restart file for a subsequent job with a larger basis set.
If you are working with a system containing metal atoms, you can set the formal charge and spin for each metal atom in an atomic section. Jaguar uses this information to guide the construction of the initial guess wave function.
Finally, try setting iacscf=1. This keyword was developed especially to aid in SCF convergence, particularly for organometallics. Note that the energy obtained with iacscf=1 can only be compared to other energies also obtained using iacscf=1. If you need to compare to energies obtained without using iacscf=1, then use the restart file from the iacscf=1 job for a new run but delete the iacscf=1 keyword before submitting the job.
If after attempting the above fixes, you still do not get convergence, send the input file in an e-mail message to email@example.com.
Keywords: Jaguar, convergence
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