Structural evolution and electronic mechanism for KBH4 phase transition from first-principles calculations

- The predicted phase transition pressure agrees well with experimental measure.
- The structural evolution of KBH4 is associated with rotation of [BH4]− cluster.
- The band gap narrows somewhat along with phase transition.
- The BH covalent bond weakens while KH interaction increases from α → β → γ phase.
- The KK anti-bonding and coulomb repulsion are stronger during phase transition.