Understanding of the Buckling Distortions in Silicene

Abstract

Silicene, the all Si analogue of graphene is structurally different due to the presence of buckling distortions in the individual six membered rings. The sufficiently strong coupling between the unoccupied molecular orbitals (UMOs) with occupied molecular orbitals (OMOs) leads to pseudo-Jahn–Teller distortion (PJT) and the characteristic buckling in silicenes. σ–π separation analyses reveal that the σ-backbone gets stabilized, whereas the π-backbone is destabilized due to buckling. However, the stabilization of puckering σ-backbone overwhelms the π-backbone destabilization. This is exactly opposite to that of graphene. The cations like Li+ can suppress the PJT distortions resulting in a planar structure. This leads to opening of band gap (∼1.62 eV). Si substituted benzenes binds more strongly with Li+ than benzene. The mutual competition/synergy between the orbital interactions of the ring with the cation and the π-charge density across the surface of molecule governs the stability of these complexes.