Theoretical investigations of phases of AlAs by first-principles

Five potential novel phases of AlAs (Pmn21-AlAs, Pbam-AlAs, Pbca-AlAs, bct-AlAs and wz-AlAs) are proposed and the stabilities of them are verified by the enthalpy, independent elastic constants and phonon dispersion spectra. The mechanical, electronic and thermodynamic properties of ten AlAs phases are studied and the electronic properties are calculated by PBE0 hybrid functional. Pmn21-AlAs and Pbam-AlAs own direct band gaps, so they have electronic advantages over other phases of AlAs at 0 GPa. Our calculated band gaps are 3.02, 3.07, 3.21, 2.76, 3.12, 1.15, 1.88, 2.53, 2.75 and 2.53 eV for Pmn21-AlAs, Pbam-AlAs, Pbca-AlAs, bct-AlAs, wz-AlAs, oC12-AlAs, hP6-AlAs, cI24-AlAs, zb-AlAs and cmcm-AlAs, respectively. Additionally, these phases: Pmn21-AlAs, Pbam-AlAs, Pbca-AlAs, bct-AlAs, cI24-AlAs, and cmcm-AlAs behave in a ductile manner, and wz-AlAs, oC12-AlAs, hP6-AlAs and zb-AlAs behave in a brittle manner. Otherwise, cmcm-AlAs has the greatest anisotropy, and hP6-AlAs has the least anisotropy.