Surface reconstructions are generally observed on covalently bonded materials, and they are not frequent on metal surfaces. Recently, quantum calculations on the Al₂Cu metallic alloy identified covalent-like Al-Al bonds [1]. In this study, we show that these covalent bondings are at the origin of a surface reconstruction for Al₂Cu(001) [2]. The bulk structure of the Al₂Cu intermetallic compound is described by graphite-like Al 6³ nets [3]. The combination of both experimental methods (STM, STS, LEED, UPS, XPS) and ab-initio computational methods (atomic relaxations, STM simulations, electronic structure calculations) gives many arguments to match the surface plane with a bulk truncated surface model terminated by incomplete Al planes. The covalent-like interaction is highlighted by ab-initio calculations: the energetic cost associated with the removal of pairs of Al atoms is the lowest for the two nearest surface Al atoms.

[1] Yu. Grin et al., J. Sol. St. Chem. 179 (2006) 1707.
[2] L.N. Serkovic Loli et al., Phys. Rev. Lett. 108 (2012) 146101.
[3] H. Nowotny and K. Shubert, Z. Metallkd. 37 (1946) 17.