Comparative study of rutile and anatase SnO2 and TiO2: Band-edge structures, dielectric functions, and polaron effects
Comparative study of rutile and anatase SnO2 and TiO2: Band-edge structures, dielectric functions, and polaron effects
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DOI：
10.1063/1.4793273
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发表时间：
2013-02-28
影响因子：
3.2
通讯作者：
Persson, Clas
中科院分区：
文献类型：
--
作者：
Dou, Maofeng;Persson, Clas
SnO 2和TiO 2多晶型物（金红石型和金红石型）是具有相似晶体结构、可比键长和电子带隙能量但具有不同光学和电子性质的氧化物。在这项工作中，我们从带边结构和电子-声子耦合研究了这些差异的根源。的带边结构，介电函数，和有效质量的计算通过第一性原理的方法与交换相关描述的混合泛函。声子频率的计算使用有限位移法与非解析校正，和声子的贡献的介电函数建模使用多声子洛伦兹模型。计算的带边结构表明，最底部的导带是高度分散的SnO 2多晶型物，但平坦的分散的TiO 2多晶型物，因为强烈本地化的Ti-3d状态。因此，SnO 2多晶型物呈现小的有效电子质量和弱的光吸收，而TiO 2多晶型物呈现强的光吸收和较大的有效电子质量。由于TiO_2与SnO_2之间存在较强的离子键，因此其Born有效电荷比SnO_2大，从而产生较强的极化子效应和较大的平均静态介电常数ε（0）。例如，金红石型TiO 2的λ（0）= 115，而金红石型SnO 2的λ（0）= 9.5。此外，有趣的是，注意到金红石型TiO 2中的η（0）比金红石型TiO 2中的η（0）大得多（η（0）= 28），尽管它们具有相同的化学组成，这与相的局部结构畸变有关。(C)2013年美国物理学会。[http：//dx.doi.org/10.1063/1.4793273]
SnO2 and TiO2 polymorphs (rutile and anatase) are oxides with similar crystal structures, comparable bond lengths, and electronic band-gap energies, but different optical and electronic properties. In this work, we have studied the origin of these differences from the band-edge structures and electron-phonon coupling. The band-edge structures, dielectric functions, and effective masses were calculated by means of a first-principles approach with the exchange-correlation described by a hybrid functional. The phonon frequencies were calculated using a finite displacement method with non-analytic correction, and the phonon contribution to the dielectric functions was modeled using a multi-phonon Lorentz model. The calculated band-edge structures show that the bottommost conduction bands are highly dispersive for SnO2 polymorphs but flat dispersive for TiO2 polymorphs because of the strongly localized Ti-3d states. Consequently, SnO2 polymorphs present small effective electron masses and a weak optical absorption, whereas the TiO2 polymorphs present a strong optical absorption and larger effective electron masses. Due to the strong ionic bonds, TiO2 have larger Born effective charges than that of SnO2, result in stronger polaron effect and larger average static dielectric constant epsilon(0). For example, epsilon(0) = 115 for rutile TiO2 whereas epsilon(0) = 9.5 for rutile SnO2. Moreover, it is interesting to note that the epsilon(0) in rutile TiO2 is much larger than in anatase TiO2 (epsilon(0) = 28) although they have the same chemical compositions, which related to the local structure distortion of the phases. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793273]