Electronic and atomic structure of surface oxides
Abstract
Copper metal-oxide interfaces are important systems of high technological relevance (steels, superalloys). The structure of oxide films at low-index surfaces of metallic Cu is a topic investigated with advanced experimental and theoretical techniques. Such techniques are employed here to stuldy the so-called ‘29’ superstructure that forms on a clean Cu(111) surface upon exposure to oxygen and subsequent annealing. Its surface cell denoted as √13 R46.1°×7 R21.8° is 29 times bigger than the unit cell of clean Cu(111) [1]. This structural complexity requires a combined effort between experimental investigations and computational modeling to achieve the required degree of accuracy [2-4]. Based on experimental data, we devised and tested different models of the ‘29’ superstructure in the previous rounds of this project, NAISS 2023/5-76 and 2024/5-196.
To refine the computational methodology, we started with clean low-index surfaces of Cu, (111), (110), and (100) using VASP and projector augmented wave (PAW) type pseudopotentials [5,6]. The structural models were built; the computational parameters have been refined to reliably achieve convergent results. Surface core level shifts were computed [7] by comparing the total energies of slabs with impurities [core holes or equivalent Z+1 (Zn) or Z+2 (Ga) species] in the bulk and in the outermost surface layers. In the continuation, we will employ DFT modeling [5-9] to study the clean and early-stage oxidized surfaces of copper, to aid the corresponding experimental studies conducted at CoESCA beamline at BESSY II in March 2025 using Auger Photoelectron Spectroscopy (APECS) to measure the 3d double hole energies with high accuracy [2-4]. By adding the kinetic energies of the photoelectrons and the Auger electrons very accurate double hole energies can be determined. In the computational modeling of Cu(111) oxidized surface, the focus will be made on the dynamical effects for which ab initio molecular dynamics (AIMD) runs will be employed.
The results of these studies are of relevance to materials for advanced batteries and may accelerate the development of that field. The methodologies developed for the oxidized copper surfaces will be useful in studies of oxidized surfaces of other metals and alloys (such as Al-based) of industrial relevance.
References
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