過渡金屬氧化物中，電荷、自旋及晶體結構等屬性，皆與價電子軌域對稱性有關，因為它們的電子電荷與自旋彼此間的交互作用，以及晶體結構上的轉變，產生如：高溫超導、龐磁阻效應及金屬絕緣相變等物理特性。所以，探討過渡金屬氧化物價電子在晶體中的對稱性，是研究強關聯電子系統的重要方法。 此篇論文主要藉由計算Fe3O4之電子結構，瞭解LDA+U近似法，是否可正確描述半金屬材料之能帶結構；進而計算此半金屬材料特有之電荷、自旋及軌域有序性。另一方面，我們也進行兩種不同晶體結構之Mn3O4電子結構計算，並比較Fe3O4之結果。最後，我們將比較計算Fe3O4摻雜Al系統總能之高低，以判斷Al原子所取代之最佳位置。 All unique properties of charges, spins and crystal structures of transition metal-oxides can attribute to their symmetrical valence electron orbital. Indeed, many important features, such as high temperature superconductivity, colossal magnetoresistance effect and metal-insulator transition are in closely connection to the complicate charge-spin interaction. Therefore, in this thesis, we will investigate the electronic structure of these strongly correlated systems by means of first-principles calculations.
In this work, we firstly performed the electronic structure calculation of Fe3O4. Beyond the DFT, LSDA+U approximation was also adopted to elucidate the characteristics of this half-metal material. Furthermore, charge, spin, and orbital ordering in a half-metal were studied carefully with proper coordinate consideration. On the other hand, the electronic structure calculations corresponding to different crystal structures were carried out in our work. Finally, the optimized doping site of Al in Al-doped Fe3O4 can be determined from calculated total energies.
