A detailed study of the (001) surface of the ${\mathrm{Al}}_2\mathrm{Cu}$ crystal using both experimental and ab initio computational methods is presented in this work. The combination of both approaches gives many arguments to match the surface plane with a bulk truncated surface model terminated by incomplete Al planes. The missing rows of Al atoms lead to a $2\sqrt{2}\times \sqrt{2}R$ 45° surface reconstruction with two domains rotated by 90° from each other. Ab initio calculations demonstrate that the energetic cost associated with the removal of pairs of Al atoms is the lowest for the two nearest surface Al atoms (covalentlike interaction). They reveal that the remaining atomic rows of various widths are oriented according to the graphitelike Al $6^3$ nets used to describe the ${\mathrm{Al}}_2\mathrm{Cu}$ bulk structure. The surface dynamics observed at 300 K at the ${\mathrm{Al}}_2\mathrm{Cu}$ surface is also presented. Finally, configurational and vibrational entropies are introduced to discuss the reduced surface plane density.

• Received 9 August 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.146101