  Despite the recent progress on two-dimensional multilayer materials (2DMM)
with weak interlayer interactions, the investigation on 2DMM with strong
interlayer interactions is far from its sufficiency. Here we report on
first-principles calculations that clarify the structural evolution and
optoelectronic properties of such a 2DMM, multilayer silicene. With our newly
developed global optimization algorithm, we discover the existence of rich
dynamically stable multilayer silicene phases, the stability of which is
closely related to the extent of sp3 hybridization that can be evaluated by the
average bonds and effective bond angles. The stable Si(111) surface structures
are obtained when the silicene thickness gets up to four, showing the critical
thickness for the structural evolution. We also find that the multilayer
silicene with pi-bonded surfaces present outstanding optoelectronic properties
for the solar cells and optical fiber communications due to the incorporation
of sp2-type bonds in the sp3-type bonds dominated system. This study is helpful
to complete the picture of structure and related property evolution of 2DMM
with strong interlayer interactions.
