OS1123 Phase-transition analysis of lithium niobate based on first-principles lattice dynamics
Details
The ferroelectric phase transition of lithium niobate (LiNbO_3) has theoretically been analyzed using lattice vibrational analyses based on first-principles calculations. The phonon dispersion relation of the paraelectric phase has four imaginary vibrational modes at the vicinity of the Γ point, which have imaginary frequencies in the wide region of the Brillouin zone including the zone boundaries. This suggests that the ferroelectric phase transition in LiNbO_3 is not the conventionally-accepted displacive type but should be a complicated mixture of displacive and order-disorder type.
