Comparative study between TB-mBJ and GGA+U on magnetic and optical properties of CdFe 2 O 4
Comparative study between TB-mBJ and GGA+U on magnetic and optical properties of CdFe 2 O 4
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TB-mBJ与GGA U对CdFe 2 O 4 磁光学性能的对比研究
DOI：
10.1016/j.jmmm.2015.05.032
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发表时间：
2015
影响因子：
2.7
通讯作者：
A. Kenz
中科院分区：
文献类型：
--
作者：
H. Zaari;A. Hachimi;A. Benyoussef;A. Kenz
采用基于密度泛函理论（DFT）的全势线性增广平面波（FP-LAPW）方法研究了块状尖晶石型铁氧体CdFe 2 O 4的态密度、光学性质和XMCD性质。广义梯度近似（GGA）求解交换关联势时低估了带隙值，因此需要用两种方法对GGA进行修正：Tran-Blaha修正的Becke-Johnson交换势近似（TB-mBJ）和GGA+多轨道平均场Hubbard势（GGA+U）。这些方法提供了准确的计算结果，其光学性质和带隙与实验数据吻合良好，CdFe 2 O 4在可见光范围内的吸收系数大于104/cm。用GGA+ U和TB-mBJ计算的第一个临界点（光吸收边）分别位于1.56 eV和1.88 eV处. XMCD谱在L3边出现一个双峰，表明Fe ~（2+）和Fe ~（3+）同时存在，占据八面体位置.然而，使用GGA+ U的原子的电荷是很好地本地化，随后的双峰不会reproduction.The晶体场创建额外的水平，提供在可见光辐射，具有这些属性，这种化合物促进其用于设备的应用程序运行在一个宽的能量范围内的基础上CdFe 2 O 4在光电子学。
Full Potential Linearized Augmented Plane Wave (FP-LAPW) based on density functional theory (DFT) is carried out to study the density of states, optical properties and XMCD properties of bulk spinel ferrite CdFe2O4. The exchange correlation potential was solved by Generalized Gradient Approximation (GGA) that underestimates the band gap value, therefore, the later needed to be corrected using two approaches: Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) and GGA plus the multi-orbital mean-field Hubbard potential (GGA+U). These methods provide accurate results in good agreement for the optical properties and band gap with experimental data.CdFe2O4has a coefficient of absorption more than 104/cm in the visible range. The first critical point known as optical absorption edge calculated with GGA+Uand TB-mBJ appears at 1.56 eV and 1.88 eV, respectively.The XMCD spectra show a double pic in L3edge indicating the presence of both Fe2+and Fe3+ions, occupying the octahedral sites. However, using GGA+Uthe charge of the atoms is well localized and subsequently the double peak does not reproduce.The crystal field creates additional levels that provide radiation in the visible, having these properties; this compound promotes its use for device applications operating over a wide energy range based on CdFe2O4in optoelectronics.