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基于第一性原理的赝势平面波方法计算了完整YTaO_4和LuTaO_4晶体的电子结构、介电函数、折射率、吸收光谱。计算结果表明,二者价带的贡献都主要来源于O2p态。导带分为两部分,下导带都主要由Ta5d态组成,YTaO_4上导带主要由Y4d态组成。而LuTaO_4上导带的贡献主要来源于Lu5d态。在ω=0时,YTaO_4和LuTaO_4晶体的介电常数和折射率都非常接近;介电函数虚部的低能特征峰(小于10.0 eV)归因于TaO_4~(3-)基团的电子跃迁,对应电子从O2p价带到Ta5d导带的跃迁;10.0～15.0 eV之间的特征峰对应于电子从价带到上导带的跃迁;大于15.0 eV的特征峰则归因于O2s态的内层电子到导带的跃迁。两种晶体在紫外区的吸收带宽而强,此吸收带归属于从氧(2p)到钽d~0离子的电荷转移跃迁。
The electronic structure, dielectric function, refractive index and absorption spectrum of intact YTaO_4 and LuTaO_4 crystals were calculated based on the first-principles pseudopotential plane wave method. The calculation results show that the contribution of both valence bands mainly comes from the O2p state. The conduction band is divided into two parts, the lower conduction band is mainly composed of Ta5d state, YTaO_4 conduction band is mainly composed of Y4d state. The contribution of the conduction band on LuTaO_4 mainly comes from the Lu5d state. The dielectric constant and refractive index of YTaO_4 and LuTaO_4 crystal are very close to each other when ω = 0. The low energy peak (less than 10.0 eV) of imaginary part of dielectric function is attributed to the electronic transition of TaO_4 ~ (3-) Corresponds to the transition from the O2p valence to the Ta5d conduction band; the characteristic valence between 10.0 and 15.0 eV corresponds to the transition from the valence band to the upper conduction band; the characteristic peak greater than 15.0 eV is attributed to the inner layer of the O2s state Electronic to conduction band transition. Both crystals have a strong absorption band in the ultraviolet region, which belongs to the charge transfer transition from oxygen (2p) to tantalum d ~ 0.