The ab initio tensile test has been applied to an Al Σ9 grain boundary by using the ab initio pseudopotential method. The theoretical tensile strength is 9.50 GPa at the strain 21%. As compared with the theoretical tensile strength in the direction [001] or [111] of an Al single crystal, the boundary is still strong due to the interface reconstruction. The interface extends at almost the same rate with the bulk interlayer until the strain of 19% in spite of the reduced number of interfacial bonds, which indicates the special strength of the reconstructed bonds. This feature can be regarded as a typical property of Al that strong local bonds are formed for less-coordinated atoms at defects.

• Received 29 December 2003

DOI:https://doi.org/10.1103/PhysRevB.69.134106