Abstract
The electronic, optical, and lattice dynamical properties of tetracalcium trialuminate (Ca4Al6O13) with a special sodalite cage structure were calculated based on the density functional theory. Theoretical results show that Ca4Al6O13 is ductile and weakly anisotropic. The calculated Young’s modulus and Poisson ratio are 34.18 GPa and 0.32, respectively. Ca4Al6O13 is an indirect-gap semiconductor with a band gap of 5.41 eV. The top of the valence band derives from O 2p states, and the bottom of conduction band consists of Ca 3d states. Transitions from O 2p, 2s states to empty Ca 4s, 3d and Al 3s, 3p states constitute the major peaks of the imaginary part of the dielectric function. Ca4Al6O13 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.
Highlights
Calcium aluminates are a series of inorganic compounds obtained by sintering calcium oxide and alumina at high temperatures
The electronic structures, mechanical behaviors, and optical properties of Ca4 Al6 O13 (CAO) crystal were studied in this work
CAO belongs to the cubic system
Summary
Calcium aluminates are a series of inorganic compounds obtained by sintering calcium oxide and alumina at high temperatures They have a wide variety of allotropes and different geometric structures, and are mainly used for refractory materials, calcium aluminate cements, optoelectronic devices, etc. Monocalcium hexa-aluminate (CaAl12 O19 ) belongs to the hexagonal crystal system, and is mainly used in high-temperature refractory materials [7,8]. Materials 2018, 11, x FOR PEER REVIEW determined by Lars Peters et al [15] belongs to the cubic system with a special sodalite cage discovered, there is a lack of detailed investigations on its physiochemical properties and potential structure, and appears in some chemical reactions [16]. Situations, such as high alumina cements, photoelectric devices, and so on
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