First-principles study on phases of AlP

Four potential novel phases of AlP (Pmn21-AlP, Pbam-AlP, Pbca-AlP and bct-AlP) are proposed in this study and the stabilities are verified by the enthalpy, independent elastic constants and phonon dispersion spectra. The electronic and mechanical properties of ten AlP phases are studied and the electronic properties are calculated by hybrid functional. All the ten phases possess the properties of semiconductor. Pmn21-AlP and Pbam-AlP have electronic advantages over wz-AlP and zb-AlP at 0 GPa for their direct band gaps. Our calculated band gaps are 3.22, 3.27, 3.47, 3.04, 2.57, 0.62, 1.38, 3.34, 2.09 and 2.71 eV for Pmn21-AlP, Pbam-AlP, Pbca-AlP, bct-AlP, cI24-AlP, hR18-AlP, oC12-AlP, wz-AlP, zb-AlP, and Cmcm-AlP, respectively. Additionally, Pmn21-AlP, Pbam-AlP, Pbca-AlP, bct-AlP, cI24-AlP, hR18-AlP, wz-AlP, and Cmcm-AlP behave in a ductile manner, and oC12-AlP and zb-AlP behave in a brittle manner.