Some systems are more difficult to converge than others. A Pd slab for instance is much more easy to converge than an Iron slab. Generally what you do in a problematic case is to go for more conservative settings. One of the first things to try is to use the Convergence%Degenerate key. The two main option are to decrease SCF%Mixing and/or DIIS%Dimix. If that all does not work you can try to use temperature smearingConvergence%ElectronicTemperature (but this only works for 2D systems). Add to you input
SCF
Mixing 0.05 ! more conservative mixing
End
Diis
DiMix 0.1 ! also more conservative strategy for DIIS procedure
End
Convergence
Degenerate Default ! For most calculations this is quite a good idea anyway
ElectronicTemperature 0.03 0.01 0.003 ! Try to converge with progressively lower temperatures
End
