Comparing hydrostatic-pressure- and epitaxial-strain-induced phase transitions in multiferroic PbNiO3 from first principles

• The phase transitions of PNO are obtained in both pressure and misfit strain cases.
• A Cc phase will be adopted instead of the R3c phase by applying misfit strain.
• The P, AFD, and TN are tunable by both hydrostatic pressure and misfit strain.
• The DOS of PNO are calculated and all the phases exhibit semiconducting behavior.

First-principles calculations are performed to simulate hydrostatic pressure and misfit strain effect on PbNiO3 (PNO) material. Significant difference between hydrostatic pressure and misfit strain effect is discovered. That is (1) a hydrostatic-pressure-induced phase transition from a rhombohedral R3c phase to an orthorhombic Pnma phase emerges around 6 GPa; and (2) an epitaxial-strain-induced phase transition from a monoclinic Cc phase (the sequel to a monoclinic distortion from R3c) to an orthorhombic Pbnm phase occurs about −3.3% misfit strain. Besides, the behaviors of oxygen octahedra tilting, polarization and the magnetic ordering temperature TN have been found to be strikingly affected by the variation of hydrostatic pressure and misfit strain, respectively. Finally, origins of the induced phase transitions are revealed.