Figure 2. Interchange of Axial and Equatorial Atoms in Trigonal Bipyramidal Molecules

A: Calculated Ground State Structure for PF5
Viewing tools:
Impose a color scheme to follow the atoms undergoing exchange:
Begin and stay equatorial red
Begin equatorial and become axial orange
Begin axial and become equatorial blue

Animate one Berry Pseudo Rotation (BPR):
Takes A to B: then
Calculated Transition State
Viewing Tools:

Tools to View the (Berry) Exchange Mechanism
  2. Displacement

  3. Compare to A
  4. View one Cycle of the Vibration:
    Compare final point (b) to B. Note Step 4 is a Berry Pseudo Rotation: A to B
Impose a color scheme to follow the atoms undergoing exchange:
Begin and stay equatorial red
Begin equatorial and become axial orange
Begin axial and become equatorial blue
 B: Calculated Ground State Structure for PF5
Viewing tools:

Impose a color scheme to follow the atoms undergoing exchange:
Begin and stay equatorial red
Begin equatorial and become axial orange
Begin axial and become equatorial blue