First-principles investigation of SrBi2Ta2O9

The electronic structure of SrBi2Ta2O9 (SBT) is investigated from first-pri nciples, within the local density approximation. using the full-potential l inearized augmented plane wave (LAPW) method. The results show that, beside s the large Ta(5d)-O(2p) hybridization which is a common feature of the fer roelectric perovskites, there is an important hybridization between bismuth and oxygen states. The role played by these two covalent bonds for driving the ferroelectric instability in SBT is investigated.