Electronic structure and possible phase transition mechanism of different phases for perovskite structured AgNbO₃

Electronic structure, crystal structural evolution and elastic properties of AgNbO₃ for phases Pmc2₁, Pbcm, Cmcm, P4/mbm and Pm3m have been investigated by first-principles calculations. The differences of electronic structure among phases are caused by the various intensity of Nb-4d, O-2p and Ag-4d, 5 s orbitals hybridization. The Nb-O bond and the torsion angle of NbO₆ octahedron in different phases are investigated, and the lattice distortion can be attributed to the Jahn-teller effect. The crystal structural evolution among different phases is correlated with the phase transition closely. The elastic constant matrix of each phase satisfies the condition of mechanical stability. AgNbO₃ is the ductile material and has the largest rigidity and the strongest volumetric strain resistance in the cubic phase.