  By using first-principles calculations, we systematically investigated
several observed phases of silicene on Ag(111) substrates and their electronic
structures. We find that the original Dirac cone of silicene is about 1.5-1.7
eV deeply below the Fermi level and severely destroyed by the band
hybridization between silicene and Ag in all the examined phases. Thus,
silicene synthesized on Ag(111) substrates could not preserve its excellent
electronic property and new method is needed to develop in synthesizing
silicene with its Dirac cone surviving.
