Phase stability, mechanical properties and electronic structure of hexagonal and trigonal Ti₅Al₂C₃: An ab initio study

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• 作者：Chenliang Li ; ^{lichenliang1980@yahoo.com.cn} ; Zhenqing Wang ; Chaoying Wang
• 关键词：A. Ternary alloy systems ; E. Ab-initio calculations ; E. Phase stability ; E. Electronic structure
• 刊名：Intermetallics
• 出版年：2013
• 出版时间：February, 2013
• 年：2013
• 卷：33
• 期：Complete
• 页码：105-112
• 全文大小：814 K

文摘

This paper investigates in detail about the phase stability, mechanical and electronic properties of Ti₅Al₂C₃ in the hexagonal (H) and trigonal (T) structures using the first-principles density functional method. Through a series of calculations, including the total energy as a function of volume, the Gibbs free energy as a function of pressure, the elastic stabilities and electronic structures, we have confirmed that T-type Ti₅Al₂C₃ is more energetically stable structure than H-type. It is found that the two structures is more compressible in the c direction than along the a direction, and the hexagonal structure is easily compressed compared with the trigonal structure. It is interesting to note that the c/a ratio of T-Ti₅Al₂C₃ remains unchanged when the pressure is above 50?GPa. The studies of elastic properties show that T-Ti₅Al₂C₃ has better mechanical properties, while the H-Ti₅Al₂C₃ is more ductile than others Ti-Al-C compounds. The calculated Debye temperature and elastic anisotropic factors indicate that T-Ti₅Al₂C₃ has a higher thermal conductivity and degree of anisotropy. By examining the density of states and Mulliken analysis under various pressures, we also found that the Ti-C bonding in the two structures is stronger than the Ti-Al bonding and indicates that the Ti-C bonding is more resistant to deformation than the Ti-Al bonding. Moreover, the two structures become less stable with the pressure increasing.