Electronic structure and ferroelectricity in SrBi2Ta2O9

The electronic structure of SrBi2Ta2O9 is investigated from first-principle s, within the local-density approximation, using the full-potential lineari zed augmented plane-wave method. The results show that, besides the large T a(5d)-O(2p) hybridization which is a common feature of the ferroelectric pe rovskites, there is an important hybridization between bismuth and oxygen s tates. The underlying static potential for the ferroelectric distortion and the primary source for ferroelectricity is investigated by a lattice-dynam ics study using the frozen-phonon approach.