  Diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate,
[PF$_6$][P$_{1,2,2,4}$], is an organic ionic plastic crystal with potential
uses as a solid electrolyte in storage and light harvesting devices. In this
work we present a molecular dynamics simulation study for this material
covering an extended temperature range, from 175 K to 500 K. The simulations
predicts a transition from the crystalline to a {\em semi} plastic phase at 197
K, the onset of cation jump-like rotations at 280 K, a third transition at 340
K to a {\em full} plastic phase and melting to 450 K. Overall, the simulations
show a good agreement with the experimental findings providing a wealth of
detail in the structural and dynamic properties of the system.
