Pseudo Jahn-Teller effect in the decasilanaphthalene molecule: Towards the origin of the buckling in silicene

摘要

It has been theoretically predicted that the ground state of free-standing silicene has a periodic buckled structure, whose origin is attributed to the puckering distortion on the individual six-member rings. In this work we present a theoretical analysis of the vibronic instability of the ground state of two hexagonal silicene units (decasilanaphthalene molecule) of D2h planar symmetry to the 3D puckered structure with C-2h symmetry. Both, the multilevel superposition vibronic model and possible mixing of excited states of different irreducible representations are studied. We show that contrary to the one six-member ring case, for the decasilanaphthalene molecule, the multilevel PJT does not provide a satisfactory explanation for puckering and a proper description is given by a ground state coupling with two quasi-degenerate excited states. Hence a simple extrapolation of the origin of the puckering distortion in silicene from one to n-hexagonal components is not straightforward. (C) 2015 Elsevier B.V. All rights reserved.