Electronic structure, anisotropic elastic and thermal properties of monoclinic Ca2Nb2O7
Electronic structure, anisotropic elastic and thermal properties of monoclinic Ca2Nb2O7
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单斜晶系Ca2Nb2O7的电子结构、各向异性弹性和热性能
DOI：
10.1016/j.ceramint.2016.02.169
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发表时间：
2016
影响因子：
5.2
通讯作者：
Pan Wei
中科院分区：
文献类型：
--
作者：
Yang Jun;Zhao Meng;Shahid Muhammad;Feng Jing;Wan Chunlei;Pan Wei
采用密度泛函理论（DFT）方法研究了单斜晶系Ca 2Nb 2 O 7的电子结构、各向异性弹性和热学性质，并与实验结果进行了验证.结果表明，单斜相Ca_2Nb_2O_7是直接带隙绝缘体，其带隙计算值为3.07 eV，与实验值3.33 eV相当。导带底部（CB）主要由Nb原子的4电子和O原子的2电子组成，而价带顶部（VB）主要由O原子的2电子组成。不同方向的声速计算结果表明，在[100]和[001]方向上，快混合模（v+）的声速都远大于慢混合模（v-）和纯横模（vt）的声速。在[010]方向的三种声学模式中，纯纵模的声速最大。根据Clarke的模型，单斜Ca 2Nb 2 O 7在高温下具有1.43 Wm− 1 K − 1的低极限热导率，并且在（100）、（110）、（010）和（001）面的最小热导率敏感地取决于方向。
The electronic structure, anisotropic elastic and thermal properties of monoclinic Ca2Nb2O7have been investigated by density functional theory (DFT) calculations and further are verified by experimental results. It has been shown that the monoclinic Ca2Nb2O7is a direct band gap insulator with the calculated band gap of 3.07 eV which is comparable with the experimental value of 3.33 eV. The bottom of the conduction band (CB) is dominated by the4dorbitals of the Nb atoms and the2porbitals of O atoms, while the top of valence band (VB) mainly consists of the2porbitals of O atoms. Calculated sound velocities of different directions show that the faster mixed mode (v+) is much larger than that of slower mixed mode (v-) and pure transverse mode (vt) in both [100] and [001] directions. The pure longitudinal modevlhas the greatest sound velocity among the three acoustic modes in the [010] direction. According to Clarke's model, monoclinic Ca2Nb2O7has low limit thermal conductivity with 1.43 Wm−1K−1at high temperature, and minimum thermal conductivity in (100), (110), (010) and (001) planes sensitively depends on the directions.