POTIM-tag

$$POTIM = \mbox{for {\tt IBRION}=0, time step in fs}$$

For IBRION=1,2 or 3, POTIM serves as a scaling constant for the forces.

Default
if IBRION=0 (MD)	no default, user must supply this value
if IBRION=1,2,3 (relaxation)	0.5

POTIM supplies the time step for an ab-initio molecular dynamics ( IBRION=0), and must be entered by the user for all MD simulations.

In addition POTIM severs as a ``scaling constant'' in all minimization algorithms (quasi-Newton, conjugate gradient, and damped molecular dynamics). Especially the Quasi-Newton algorithm is sensitive to the choice of this parameter (see section IBRION 6.21).