Polaronic deformation at theFe2+/3+impurity site inFe:LiNbO3crystals
Polaronic deformation at theFe2+/3+impurity site inFe:LiNbO3crystals
复制标题
DOI：
10.1103/physrevb.91.094109
复制
发表时间：
2015-03
影响因子：
3.7
通讯作者：
A. Sanson;A. Zaltron;N. Argiolas;C. Sada;M. Bazzan;W. Schmidt;S. Sanna
中科院分区：
文献类型：
--
作者：
A. Sanson;A. Zaltron;N. Argiolas;C. Sada;M. Bazzan;W. Schmidt;S. Sanna
研究了不同铁价态的掺铁晶体。一项扩展的X射线吸收精细结构(EXAFS)光谱研究强调了铁周围局部结构的明显变化，这可以归因于小极化子的存在。特别是，当取代锂离子时，氧八面体相对于纯材料收缩，其平均铁-氧键值与赤铁矿非常相似。当添加一个电子时，它定域在Fe位置上，构型非常接近原子Feorbitals，导致氧笼的松弛。用自旋极化密度泛函理论(DFT)对同一体系进行了模拟。探讨了几种局域泛函和混合交换相关泛函的体结构性质。然后将计算扩展到赤铁矿的情况，最后扩展到Fe缺陷的情况。计算非常准确地再现了氧配体的大晶格弛豫，这与铁中心的电子俘获有关，可以解释为由于极化子的形成。计算令人满意地再现了现有的EXAFS数据，并允许估计极化子能量和缺陷的光学性质。
Iron dopedcrystals with different iron valence states are investigated. An extended x-ray absorption fine structure (EXAFS) spectroscopy study highlights evident changes in the local structure around iron that can be ascribed to the presence of small polarons. In particular, when areplaced a Li ion, the oxygen octahedron shrinked with respect to the pure material, with an average iron-oxygen bond value very similar to that ofhematite. When adding an electron, it localizes at the Fe site in a configuration very close to the atomic Feorbitals, inducing a relaxation of the oxygen cage. The same system was modelled by spin-polarized density functional theory (DFT). Several local as well as hybrid exchange-correlation functionals were probed on the bulkstructural properties. The computation is then extended to the case of hematite and finally to the Fe defect in. The calculations reproduced with good accuracy the large lattice relaxation of the oxygen ligands associated to the electronic capture at the Fe center that can be interpreted as due to the polaron formation. The calculations reproduce satisfactorily the available EXAFS data, and allow for the estimation of the polaron energies and the optical properties of the defect.