Diffraction refinement of localized antibonding at the Si(111)7×7surface

Abstract

We report an experimental refinement of the local charge density at the Si (111) 7x7 surface utilizing a combination of x-ray and high energy electron diffraction. By perturbing about a bond-centered pseudoatom model, we find experimentally that the adatoms are in an anti-bonding state with the atoms directly below. We are also able to experimentally refine a charge transfer of 0.26±0.04 e -from each adatom site to the underlying layers. These results are compared with a full-potential all-electron density functional DFT calculation.

Antiferromagnetic structures and electronic energy levels at reconstructed NiO(111) surfaces: ADFT+Ustudy

“…The ideal 1×1 surface structure as well as three prominent surface reconstruction models of octopolar, 2×2-α, and Rt3 were considered in this present work because of their stability [33][34][35][36][37][38][39]. The top view of the super cell structures is shown in Figure 1, and the side view can be found in Appendix B ( Figure A2).…”

“…Because the oxygen terminated surface has shown to be more stable than the metal terminated surface for MgO with the 2×2-α reconstruction [38,68] and also the calculated phase diagrams are nearly identical for MgO and NiO surface [39], we consider here only the oxygen terminated surface of the 2×2-α reconstruction. In addition, both Ni-terminated and O-terminated Rt3 reconstructions were considered as suggested by Ciston et al [38]. These two surfaces are actually both oxygen terminated at the atomistic level although we follow here the original naming scheme.…”

“…These two surfaces are actually both oxygen terminated at the atomistic level although we follow here the original naming scheme. Hydroxylation/hydrogenation as recently characterized in STM and THEED studies [38,39,44] were modeled by attaching hydrogen atoms on the surface of O-terminated and Ni-terminated surface, respectively. For simplicity, we use several shorthand notations throughout the following discussions.…”

“…Various types of reconstructions and surface passivation have been reported both experimentally and theoretically for the NiO(111) surface. In particular, so-called Octopolar, 2×2-α, and Rt3 appear to be stable reconstruction phases of the (111) surface [33][34][35][36][37][38][39][40][41][42][43]. Furthermore, hydrogenated and hydroxylated surfaces have been recently characterized in experiments using STM and THEED [38,39,44].…”

“…In particular, so-called Octopolar, 2×2-α, and Rt3 appear to be stable reconstruction phases of the (111) surface [33][34][35][36][37][38][39][40][41][42][43]. Furthermore, hydrogenated and hydroxylated surfaces have been recently characterized in experiments using STM and THEED [38,39,44]. Despite the potential importance of these reconstructions at the NiO(111) surface for material properties, especially for NiO nano-materials, a comprehensive investigation on how the reconstructions and experimentally-common surface passivation of hydrogenation/hydroxylation affect the surface electronic structure and magnetization is yet to be reported in literature.…”