Structural stability and thermoelectric property optimization of Ca 2 Si

• Published in: RSC advances Vol. 7; no. 15; pp. 8936 - 8943
• Main Authors: Xiong, Rui, Sa, Baisheng, Miao, Naihua, Li, Yan-Ling, Zhou, Jian, Pan, Yuanchun, Wen, Cuilian, Wu, Bo, Sun, Zhimei
• Format: Journal Article
• Language: English
• Published: 2017
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C6RA28125G

By using an
ab initio
evolutionary algorithm structure search, low enthalpy criterion as well as stability analysis, we have found that cubic
Fm
3̄
m
Ca
2
Si can be achieved under a negative external pressure, and the cubic phase is dynamically and mechanically stable at ambient conditions and high pressure. From first-principle hybrid functional calculations, we have unraveled the direct bandgap nature and bandgap variation of cubic
Fm
3̄
m
Ca
2
Si with respective to pressure. Moreover, by combining with Boltzmann transport theory and the phonon Boltzmann transport equation, we have predicted that the figure of merit
ZT
for the cubic
Fm
3̄
m
Ca
2
Si reaches the maximum value of 0.52 by p-type doping. Our results provide an interesting insight and feasible guidelines for the potential applications of cubic
Fm
3̄
m
Ca
2
Si and related alkaline-earth metals silicides as the thermoelectric materials for heat-electricity energy convertors.