Electronic structures and structural phase transition mechanism of Sr2MgWO6Sr2MgWO6 from first-principles calculations

We investigate the electronic structures of the cubic and tetragonal phases of Sr2MgWO6Sr2MgWO6. Calculated electronic structures show that the two phases are both wide indirect band gap semiconductors. Our phonon calculations indicate that the structural phase transition from cubic to tetragonal phase is because the phonon frequencies of Γ4+ modes become imaginary. Our variable cell-shape relaxation results imply that a symmetry-allowed intermediate trigonal phase could be realized.