Mechanical and thermodynamic properties of the monoclinic and orthorhombic phases of SiC_2N_4 under high pressure from first principles

作     者：苗楠茜 濮春英 何朝政 张飞武 卢成 卢志文 周大伟 

作者机构：College of Physics and Electronic Engineering Nanyang Normal University Nanochemistry Research Institute Curtin University State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences 

出 版 物：《Chinese Physics B》 (中国物理B（英文版）)

年 卷 期：2014年第23卷第12期

页      面：382-389页

核心收录：

学科分类：07[理学] 070205[理学-凝聚态物理] 0805[工学-材料科学与工程（可授工学、理学学位）] 0704[理学-天文学] 0702[理学-物理学] 

基　　金：Projected supported by the Henan Joint Funds of the National Natural Science Foundation of China(Grant Nos.U1304612,U1404608,and U1404216) the Special Fund for the Theoretical Physics of China(Grant No.11247222) the Nanyang Normal University Science Foundation,China(Grant Nos.ZX2010011,ZX2012018,and ZX2014088) the National Natural Science Foundation of China(Grant Nos.11304167 and 51374132) the Postdoctoral Science Foundation of China(Grant No.20110491317) the Young Core Instructor Foundation of Henan Province,China(Grant No.2012GGJS-152) 

主　　题：Si C2N4 density functional theory Debye temperature elastic anisotropy 

摘      要：First principles calculations are preformed to systematically investigate the electronic structures, elastic and thermodynamic properties of the monoclinic and orthorhombic phases of Si C2N4 under pressure. The calculated structural parameters and elastic moduli are in good agreement with the available theoretical values at zero pressure. The elastic constants of the two phases under pressure are calculated by stress–strain method. It is found that both phases satisfy the mechanical stability criteria within 60 GPa. With the increase of pressure, the degree of the anisotropy decreases rapidly in the monoclinic phase, whereas it remains almost constant in the orthorhombic phase. Furthermore, using the hybrid density-functional theory, the monoclinic and orthorhombic phases are found to be wide band-gap semiconductors with band gaps of about 2.85 e V and 3.21 e V, respectively. The elastic moduli, ductile or brittle behaviors, compressional and shear wave velocities as well as Debye temperatures as a function of pressure in both phases are also investigated in detail.