期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 117, 期 48, 页码 25504-25512出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp407496w
关键词
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资金
- U.S. Department of Energy, Office of Science, Division of Chemical Sciences, Geosciences, and Biosciences [48526]
- U.S. Department of Energy's Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory (PNNL)
- Department of Energy by the Battelle Memorial Institute [DE-AC06-76RLO-1830]
- William Wiley Postdoctoral Fellowship from EMSL
- U.S. Department of Energy, Office of Basic Energy Sciences of the SciDAC program [DESC0008666]
- Royal Society
- EPSRC [EP/H018328/1]
We provide a detailed theoretical analysis of the character of optical transitions and band gap reduction in (Fe1-xCrx)(2)O-3 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 alpha-Fe2O3 is found. This result is attributed predominantly to two effects: (i) the higher valence band edge for x approximate to 0.5, as compared to those in pure alpha-Fe2O3 and alpha-Cr2O3, and (ii) the onset of Cr -> Fe d-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.
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