Using scanning tunneling microscopy, low energy electron diffraction measurements, and ab initio calculations based on density functional theory, we present atomic models of the (root 13 x root 13)R13.9 degrees silicene superstructure grown on Ag(1 1 1). The STM images reveal two co-existing atomic arrangements with two different orientations of the silicene sheet relative to the Ag(1 1 1) surface. DFT calculations with and without the inclusion of van der Waals interactions show corrugated Si atomic positions for both orientations implying a significant interaction with Ag(1 1 1) surface. The electronic structure of both silicene and Ag(1 1 1) surface are sufficiently affected that new interface states emerge close to the Fermi level. (C) 2014 Elsevier B.V. All rights reserved.