First-principles prediction of ferroelastic phase transition in AlPO4

► This first-principles calculations predicted AlPO4 compound have a new phase of stishovite-like. ► It also predicted a ferroelastic transition between stishovite-like and m-CaCl2 phases. ► The ferroelastic transition was for the first time found in compounds of quartz-like ABO4. ► Some basics of this transition were investigated, including structural symmetry and soft modes. ► Phase boundary of this ferroelastic transition was calculated up to high temperature.