Optical Absorption and Band Gap Reduction in (Fe1鈥?i>xCrx)2O3 Solid Solutions: A First-Principles Study

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• 作者：Yong Wang ; Kenneth Lopata ; Scott A. Chambers ; Niranjan Govind ; Peter V. Sushko
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：December 5, 2013
• 年：2013
• 卷：117
• 期：48
• 页码：25504-25512
• 全文大小：495K
• 年卷期：v.117,no.48(December 5, 2013)
• ISSN：1932-7455

文摘

We provide a detailed theoretical analysis of the character of optical transitions and band gap reduction in (Fe_1鈥?i>xCr_x)₂O₃ solid solutions using extensive periodic model and embedded cluster calculations. Time-dependent density functional theory is used to calculate and assign optical absorption bands for x = 0.0, 0.5, and 1.0 and photon energies up to 5 eV. Consistent with recent experimental data, a band gap reduction of as much as 0.7 eV with respect to that of pure 伪-Fe₂O₃ is found. This result is attributed predominantly to two effects: (i) the higher valence band edge for x 鈮?0.5, as compared to those in pure 伪-Fe₂O₃ and 伪-Cr₂O₃, and (ii) the onset of Cr 鈫?Fe d鈥?/i>d excitations in the solid solutions. Broadening of the valence band due to hybridization of O 2p with Fe and Cr 3d states also contributes to band gap reduction.