中文摘要：

采用广义梯度近似下的密度泛函理论计算了铁电相BiFeO3以及顺电相BiFeO3的轨道占据数、电子云重叠布局数、净电荷分布和态密度. 结果表明, BiFeO3晶体出现铁电性的主要原因是： Fe原子的3d轨道和O原子的2p轨道杂化. 而且由于两相晶体结构上的差异, 铁电相BiFeO3原子间的共价性和离子性相对顺电相BiFeO3增强了,态密度图在价带区基本相同, 但是在导带区具有一定的差异性.

英文摘要：

By using density-functional theory in generalized gradient approximation （GGA）, the orbit populations, overlap populations, valence charges, density of states in ferroelectric and paraelectric BiFeO3 were calculated. It was demonstrated that the ferroelectric stability of BiFO3 could be attributed to the orbital hybridization of 2d orbit of Fe atom and 2p orbit of oxygen atom. Moreover, as a result of different crystal structures between two phases, ion and covalency are enhanced in ferroelectric BiFeO3 compared to paraelectric BiFeO3. Density of states in two phases were basically the same in valence band district, but they were different in the conduction band district.