First-principles calculations of (0 0 1)-Al//(0 0 1) interface in Al-Cu alloys: Atomic structure, bonding strength, stability and electronic properties

Using density-functional theory, the stability of the (0 0 1) Al and (0 0 1) θ' surfaces is evaluated by calculating their surface energy. The bonding strength and stability of the (0 0 1)α-Al//(0 0 1)θ' interface with four different atomic stacking sequences (Cu-HCP, Cu-OT, Al-HCP and Al-OT) are determined by first-principles tensile test and interfacial energy calculation, respectively. Results show that the stability of the (0 0 1) θ' surface is significantly weaker as compared to the (0 0 1) Al surface. The interface with the HCP stacking sequence is the most stable geometry and possesses the lowest interfacial energy and the strongest interface bonding. A relationship is established among the interface bonding strength, interfacial energy and interface stability. The interface with larger the interface bonding strength possesses smaller interfacial energy and higher interface stability. Analysis in terms of the electronic structure shows that the average absolute value of Bader charge of terminating Cu (or Al) of the (0 0 1) θ' surface is quite large, which results in the weak stability of the (0 0 1) θ' surface. The high bonding strength and stability for the interface with the HCP stacking sequence are ascribed to the strong charge accumulation between atoms across the interface.