Interaction of Pd withα−Al2O3(0001):

Abstract

The Pd/␣-Al 2 O 3 (0001) interface at low Pd coverage has been studied by a variety of theoretical methods and models at this metal-oxide interface. All results are consistent and predict a noticeable interaction dominated by the metal polarization in response to the presence of the substrate. A significant contribution of the charge transfer from the transition metal to the surface is also observed. The periodic fully relaxed calculations show that the most favorable adsorption site for the interaction of Pd with corundum involves the anionic surface sites, in particular the on-top oxygen site. It is also shown that adsorption of Pd atoms on the surface induces a significant relaxation of the aluminum oxide substrate, especially for the outermost aluminum layer. The small differences observed in the adsorption energies near the oxygen atoms suggest a high mobility of Pd atoms on the surface.

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

“…Thanks to this bond reorganization, the Au-alumina adsorption energy increases to 2.1 eV, which compares to 0.8 eV for bulk Al 2 O 3 (0001). 380 A similar mechanism has been predicted for the Au adsorption on Ti-doped silica films. Also here, a Ti-O bond is broken in order to form a new Ti-Au bond.…”

“…A similar situation is encountered for Au attachment to other inert oxide surfaces. 316,380 In contrast, if only the vanadyl oxygen is removed, the Au binds with 2.04 eV to the hence unsaturated V ion. The strong bonding in this case is mediated by V 3d -Au 6s / 5d hybridization, which shifts the center of the Au 6s/5d level to -1.2 eV below E F (Fig.…”

Surface model and exchange-correlation functional effects on the description of Pd/α-Al2O3(0001)

“…Similarly, the nature of the interaction between Pd and the ␣-Al 2 O 3 (0001) has been investigated by Gomes et al 15 using a cluster model and the constrained space orbital variation method. The cluster results suggest a large adsorbate-induced relaxation that has been confirmed by the same authors through periodic supercell GGA calculations within a plane wave basis set.…”

“…In general these questions can only be addressed by systematic studies of the variation of particular results with model size. However, one might expect that the interaction of Pd with ␣-Al 2 O 3 (0001), which induces a large substrate relaxation, 15 will converge more slowly with respect to model size than Pd on a simple oxide surface such as MgO.…”

Accounting for van der Waals interactions between adsorbates and surfaces in density functional theory based calculations: selected examples

“…For instance, clusters embedded in large arrays of point charges and effective core potentials (ECP) were proven to be quite useful to study metal oxide surfaces such as those of MgO 58,59 or a-Al 2 O 3 . [60][61][62] An example of an embedded cluster model with three different regions that was used to model the MgO(100) surface is shown in Fig. 1.…”