First-principles statistical mechanics approach to step decoration at surfaces

Abstract

Using a first-principles parameterized lattice-gas Hamiltonian we study the adsorbate ordering behavior at atomic steps of a Pd(100) surface exposed to an oxygen environment. We identify a wide range of gas-phase conditions comprising near atmospheric pressures and elevated temperatures around 900 K, in which the step is decorated by a characteristic O zigzag arrangement. For catalytic processes like the high-temperature combustion of methane that operate under these conditions our approach thus provides first insight into the structure and composition at a prominent defect on the working surface.

Oxide−Metal Nanowires by Oxidation of a One-Dimensional Mn−Pd Alloy: Stability and Reactivity

“…Here, at 0.1 ML Mn coverage, a composite (mixed) surface is observed (Figure a), where some of the step edges are decorated by straight and narrow lines of bright protrusions and others by rows bearing more widely spaced sequences of bright maxima. In the close-up image (7 nm ×7 nm) presented in Figure b, the latter features are identified as oxygen decorated Pd steps, by analogy with the STM images recorded after oxidation of the clean stepped Pd(1 1 9) surface: zigzag rows with ×2 periodicity are formed, attributed to Pd step atoms twofold coordinated to oxygen atoms. , The narrow line structures have, instead, ×1 periodicity (see inset of Figure b) and are ascribed to manganese oxide (MnOx) nanowires. At a Mn coverage of 0.2 ML, only the ×1 MnOx nanowires decorate the step edges of the vicinal surface (Figure c).…”

Magneto‐Optical Properties of Oxidized Co Nanowires on Pt Substrate

“…For this purpose, different structural models were considered following the selective oxidation approach of the step edges on a vicinal Pt(111) surface proposed experimentally. [ 12,13 ] Figure 1 shows the most energetically preferable models of oxide Co NWs which correspond to low oxidation state of platinum surface with degree of oxygen coverage 0.1 atomic monolayer (ML)‐CoO NW, with one oxygen atom per calculation cell (Figure 1a,b) and CoO 2 NW with four oxygen atoms per cell, corresponding to the high oxidized state of platinum surface with degree of oxygen coverage 0.4 atomic ML (Figure 1c,d). [ 13,14 ] At first, we have studied the magnetic properties of pure and oxidized Co NWs.…”

“…We have performed a firstprinciples study of the effect of oxidation on the magneto-optical properties of step-decorated Co NWs on vicinal Pt(111) surface since these nanoscale objects have been extensively studied in the last years. [7,[12][13][14] The 3D supercell with periodic boundary conditions was constructed to model the structure of step supported oxide NWs. The supercell contains a 5-atomic layer slab of Pt(111) substrate with Co NW placed at the step edge of Pt(111) surface and separated by a vacuum region of 12 Å.…”

Prediction of New Stable Compounds and Promising Thermoelectrics in the Cu–Sb–Se System

“…The cluster expansion (CE) method − has been long used to identify unknown structures in bulk materials, − surfaces − and surface adsorptions. − The crystal structure is represented by a three-dimensional lattice, in which any system state is defined by the occupation of sites in the lattice and the total energy of any configuration (σ) is expanded in series over discrete interactions (the effective cluster interactions, or ECI) between the lattice sites. where in a binary alloy ( A 1– x B x ), S i = 1 or −1 indicate whether site i in the lattice is occupied by an atom of type A or B, respectively. J α are effective cluster interactions, for a cluster of sites α (e.g., pairs, triplets, etc).…”