  Density-functional theory calculations are used to verify the atomic
structure of the $\sqrt{3}$$\times$$\sqrt{3}$ silicene phase grown on the
Ag(111) surface. Recent experimental studies strongly suggested that the
previous double-layer silicene model should be replaced with a Ag-mixed
double-layer model resembling the top layers of the
Ag/Si(111)-($\sqrt{3}$$\times$$\sqrt{3}$) surface. In our calculations, the
Ag-mixed double-layer model is indeed energetically favored over the
double-layer silicene model and well reproduces the reported scanning-tunneling
microscopy and spectroscopy data. Especially, the structural origin of the
experimental band structure is clarified as the top Ag-Si mixed layer, unlike
the experimental interpretations as either a silicene layer or the Ag(111)
substrate.
