A comprehensive analysis of the (R13xR13)R13.9{\deg} type II structure of silicene on Ag(111)

In this paper, using the same geometrical approach than for the (2R3x2R3) R30{\deg} structure (H. Jamgotchian et al., 2015, Journal of Physics. Condensed Matter 27 395002), for the (R13xR13)R13.9{\deg} type II structure, we propose an atomic model of the silicene layer based on a periodic relaxation of the strain epitaxy. This relaxation creates periodic arrangements of perfect areas of (R13xR13)R13.9{\deg} type II structure surrounded by defect areas. A detailed analysis of the main published experimental results, obtained by Scanning Tunneling Microscopy and by Low Energy Electron Diffraction, shows a good agreement with the geometrical model.Comment: 20 pages, 9 figure

Peak positions and shapes in neutron pair correlation functions from powders of highly anisotropic crystals

The effect of the powder average on the peak shapes and positions in neutron pair distribution functions of polycrystalline materials is examined. It is shown that for highly anisotropic crystals, the powder average leads to shifts in peak positions and to non-Gaussian peak shapes. The peak shifts can be as large as several percent of the lattice spacing

Physics And Chemistry Of Silicene Nano-Ribbons

We review our recent discovery of silicene in the form of silicon nano-ribbons epitaxially grown on silver (1 1 0) or (1 0 0) surfaces, which paves the way for the growth of graphene-like sheets. We further draw some perspectives for this unique novel material upon mild hydrogenation. © 2009 Elsevier B.V

Structure and melting of submonolayer ethane films on graphite

URL:http://link.aps.org/doi/10.1103/PhysRevLett.43.1878 DOI:10.1103/PhysRevLett.43.1878Elastic neutron diffraction has been used to study the structure and melting of submonolayer ethane films physisorbed on exfoliated graphite. Analysis of the relative intensity of seven Bragg reflections of the film yields the molecular orientation in the close-packed solid structure observed below 63 K. At higher temperature a novel melting process occurs which we tentatively interpret as a first-order transition to an intermediate phase followed by continuous transition to the disordered state.We acknowledge partial support of this research by the National Science Foundation under Grant No. DMR-7905958, the NATO Research Grants Program, the Petroleum Research Fund administered by the Amnerican Chemical Society, a Dow Chemical Company Grant of the Research Corporation, the University of Missouri Research Concil, and the University of Missouri Research Reactor Facility. One of us (G.J.T.) is in receipt of an American Chemical Society - Petroleum Research Fund Fellowship

The structure of atomic sulfur phases on Au(111)

The structural phases formed by atomic sulfur on Au(111) due to reaction with molecular S-2 have been investigated by qualitative low-energy electron diffraction (LEED), scanning tunneling microscopy, and normal incidence X-ray standing wavefield absorption (NIXSW) combined with X-ray photoelectron spectroscopy (XPS). Three phases are identified with increasing coverage, namely, a newly identified (5 x 5) phase, a (root 3 x root 3)R30 degrees phase, and a "complex" phase. The (5 x 5) phase, with a LEED pattern having the appearance of a "split-spot" (root 3 x root 3)R30 degrees pattern, is interpreted in terms of local (root 3 x root 3)R30 degrees ordering within a (5 x 5) ordered domain structure. The S atoms in the (5 x 5) phase occupy fcc hollow sites 1.56 A above the outermost extended Au(111) bulk atomic scatterer plane. A specific model of the ordering in this phase is proposed that, together with the observed marginal stability of the true, long-range-ordered, (root 3 x root 3)R30 degrees phase, indicates significant short-range S-S repulsion and probably compressive surface stress. The complex phase, that coexists in a poorly ordered state with the lower coverage atomic chemisorption phases, is interpreted in terms of an incommensurate long-range periodicity, but the NIXSW data shows clear evidence of local commensuration, with the S atoms mainly close to atop sites relative to the underlying Au(111) substrate; these data provide strong support for a previously proposed model based on a sulfide layer of stoichiometry AuS