摘要
基于第一性原理,计算了MgSiP_2的能带结构,结果显示压强减小了能带带隙值,部分电子有效质量随着压强增大而减小。费米能级附近电子态密度计算结果显示:随着压强的增大,价带顶电子态密度的斜率逐渐减小,而导带底电子态密度的斜率逐渐增加。结合半经典玻耳兹曼理论,分别计算了p型和n型MgSiP_2的电导率与弛豫时间的比值、赛贝克系数以及功率因子与弛豫时间的比值。结果发现:压强所致部分电子有效质量的减小,提高了p型和n型MgSiP_2的电导率,但在一定程度上降低了MgSiP_2的赛贝克系数。在压强作用下,相对于n型MgSiP_2,p型MgSiP_2的电导率增加幅度更大,补偿了压强所致p型MgSiP_2赛贝克系数的降低,提高了p型MgSiP_2的功率因子,使其大于n型MgSiP_2的对应值。计算结果表明,通过增大压强可以提高p型MgSiP_2的热电性能,为实验制备具有良好热电性能MgSiP_2提供了指导方案。
The band structures of MgSiP2 under different pressures were investigated by using first-principles calculations.It was found that the band gap and some of electron effec-tive mass of MgSiP2 decrease with the increase of pressure.The results of the density of electronic state (DOS) near the Fermi level show that the slope of DOS decreases with the increases of pressure at the top of valence band,while it shows a contrary trend at the bot-tom of conduction band.The thermoelectric properties of p-type and n-type MgSiP2 were cal-culated using the semi-classical Boltzmann transport theory.The results show that both the electric conductivities of p-type and n-type MgSiP2 increase with respect to pressure,while the Seebeck coefficients decrease with respect to pressure due to the decrease of electron ef-fective mass.Although the Seebeck coefficients decrease under pressure,the enhancement of electric conductivity of p-type is more obvious than that of n-type MgSiP2 ,resulting in the enhancement of power factor of p-type MgSiP2 under pressure.The power factor of p-type MgSiP2 is higher than that of n-type MgSiP2 .These insights point to alternative pathways to enhance the thermoelectric properties of MgSiP2 materials.
作者
戴姗
刘运牙
杨振华
DAI Shan;LIU Yun-ya;YANG Zhen-hua(School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105,China;Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan 411105,China;Kvey Laboratory of Materials Design and Preparation Technology of Hunan Province, Xiangtan University, Xiangtan 411105,China)
出处
《现代应用物理》
2016年第2期70-76,共7页
Modern Applied Physics
关键词
MgSiP2
电子结构
热电性能
第一性原理计算
MgSip
electronic structure
thermoelectric properties
first-principles calculations
