VASP’s optimization timestep

Vaspwiki describes the effect of POTIM in ionic optimization with the RMM-DIIS method (IBRION=1):

The choice of a reasonable POTIM is also important and can speed up calculations significantly, we recommend to find an optimal POTIM using IBRION=2 or performing a few test calculations.

In ionic relaxation with the conjugate gradient algorithm (IBRION=2), the stride of optimization steps are written to OUTCAR as opt step. For example,

opt step  =   0.27850  (harmonic =   0.27850) maximal distance =0.00000028

References