Fcc-to-bct phase transformation of aluminum under triaxial stresses: an ab initio constant pressure study

We have carried out constant pressure ab initio simulations within a generalized gradient approximation to investigate the response of aluminum to triaxial stresses and found that aluminum undergoes a phase transformation from the face-centered cubic structure (fcc) to a body centered tetragonal (bct) structure having the space group of I4/mmm. The critical stress for the fcc-to-bct transformation increases as the ratio of the triaxial stress increases but such a phase transition never occurs under hydrostatic compression. The bct phase is elastically unstable.