Science Advances

Supplementary Materials

This PDF file includes:

  • table S1. Calculated zero-temperature total energy differences between the tetragonal P4mm, orthorhombic Pbnm, and monoclinic Pc phases at zero pressure using several DFT exchange-correlation functionals.
  • I. Supplementary discussion: The role of the exchange correlation energy
    functional
  • II. Supplementary discussion: Spin-phase transitions under pressure
  • III. Supplementary data
  • fig. S1. Spin properties and spin-phase transitions under pressure calculated in BiCoO3.
  • fig. S2. Enthalpy energy differences between several crystal structures and the tetragonal P4mm phase calculated at T = 0 K with the PBE+U functional and expressed as a function of pressure.
  • fig. S3. Quasi-harmonic Helmholtz free energy calculated in the tetragonal P4mm, orthorhombic Pbnm, and monoclinic Pc phases at zero pressure; the
    corresponding magnetic spin orders are AFM(C), AFM(G), and AFM(G), respectively.
  • fig. S4. Analysis of SP coupling in the tetragonal P4mm phase at the special pointΓ.
  • fig. S5. Analysis of SP coupling in the orthorhombic Pbnm phase at the special point Γ.
  • fig. S6. Analysis of SP coupling in the tetragonal P4mm phase over the corresponding Brillouin zone.
  • fig. S7. Analysis of SP coupling in the orthogonal Pbnm phase over the corresponding Brillouin zone.
  • fig. S8. AFM(C) magnetic spin order parameter calculated in the tetragonal P4mm phase as a function of pressure and temperature.
  • fig. S9. AFM(G) magnetic spin order parameter calculated in the orthorhombic Pbnm phase as a function of pressure and temperature.
  • fig. S10. Volume per formula unit calculated in BCO’s polymorphs at a fixed pressure of Pf = 2.5 GPa and expressed as a function of temperature.
  • fig. S11. Calculated quasi-harmonic free energies of BCO’s polymorphs at a fixed pressure of Pf = 2.5 GPa.
  • fig. S12. Contributions to the Gibbs free energy difference, ΔGharmGP4mmharmGPbnmharm, calculated in bulk BCO as a function of temperature and pressure.
  • fig. S13. Spin free energy difference between the P4mm and Pbnm phases calculated at P = 2.5 GPa as a function of temperature.
  • fig. S14. Chemical doping strategy proposed to bring the multiferroic phase competition disclosed in bulk BCO down to zero pressure (oxygen atoms, not indicated in the figure, always enter the formulae as “O3”).
  • fig. S15. Phonon spectrum calculated in the Bi3/4La1/4CoO3 compound at zero pressure in the tetragonal P4mm phase.
  • fig. S16. Phonon spectrum calculated in the Bi3/4La1/4CoO3 compound at zero pressure in the orthorhombic Pbnm phase.
  • References (31–36)

Download PDF

Files in this Data Supplement: