Mei Huayue, Zhong Yuhan, Wang Peida, Jia Zhenyuan, Li Chunmei, Cheng Nanpu
Faculty of Materials and Energy, Southwest University, 2#Tiansheng Road, Beibei, Chongqing 400715, China.
Materials (Basel). 2018 Mar 19;11(3):449. doi: 10.3390/ma11030449.
The electronic, optical, and lattice dynamical properties of tetracalcium trialuminate (Ca₄Al₆O) with a special sodalite cage structure were calculated based on the density functional theory. Theoretical results show that Ca₄Al₆O is ductile and weakly anisotropic. The calculated Young's modulus and Poisson ratio are 34.18 GPa and 0.32, respectively. Ca₄Al₆O is an indirect-gap semiconductor with a band gap of 5.41 eV. The top of the valence band derives from O 2 states, and the bottom of conduction band consists of Ca 3 states. Transitions from O 2, 2 states to empty Ca 4, 3 and Al 3, 3 states constitute the major peaks of the imaginary part of the dielectric function. Ca₄Al₆O is a good UV absorber for photoelectric devices due to the high absorption coefficient and low reflectivity. The lattice vibration analysis reveals that O atoms contribute to the high-frequency portions of the phonon spectra, while Ca and Al atoms make important contributions to the middle- and low-frequency portions. At the center of the first Brillouin zone, lattice vibrations include the Raman active modes (E, A₁), infrared active mode (T₂), and silentmodes (T₁, A₂). Typical atomic displacement patterns were also investigated to understand the vibration modes more intuitively.
基于密度泛函理论计算了具有特殊方钠石笼结构的四钙铝酸盐（Ca₄Al₆O）的电子、光学和晶格动力学性质。理论结果表明，Ca₄Al₆O具有延展性且各向异性较弱。计算得到的杨氏模量和泊松比分别为34.18 GPa和0.32。Ca₄Al₆O是一种间接带隙半导体，带隙为5.41 eV。价带顶源于O 2态，导带底由Ca 3态组成。从O 2、2态到空的Ca 4、3和Al 3、3态的跃迁构成了介电函数虚部的主要峰值。由于高吸收系数和低反射率，Ca₄Al₆O是一种适用于光电器件的良好紫外线吸收剂。晶格振动分析表明，O原子对声子谱的高频部分有贡献，而Ca和Al原子对中低频部分有重要贡献。在第一布里渊区中心，晶格振动包括拉曼活性模式（E、A₁）、红外活性模式（T₂）和非活性模式（T₁、A₂）。还研究了典型的原子位移模式，以便更直观地理解振动模式。
