Elastic Properties, Phonon Focusing and Electronic Structures of Typical Long-Period Superstructures Al₅Ti₂ and Al₁₁Ti₅

Abstract:

The first-principles calculations were performed to systematically study the elastic properties, phonon focusing and electronic structures of typical long-period superstructures Al₅Ti₂ and Al₁₁Ti₅. The obtained lattice parameters are in good agreement with the experimental data. The elastic constants were calculated, and bulk modulus B, shear modulus G, Young’s modulus E and Poison’s ration ν were further obtained. Both of the numerical indicators and the three dimensional images show that Al₅Ti₂ and Al₁₁Ti₅ are anisotropic, and the anisotropy is slightly high for Al₅Ti₂. Three slowness surfaces were constructed for Al₅Ti₂ and Al₁₁Ti₅ to investigate the phonon focusing patterns, and the group velocity surfaces were also obtained to gain more insight into the elastic anisotropy. Due to elastic anisotropy, both of the slowness surfaces and the group velocity surfaces are nonspherical, and the anisotropy is highest for slow transverse mode, and then followed by fast transverse mode and longitudinal mode. The electronic density of states and charge density distribution of Al₅Ti₂ and Al₁₁Ti₅ indicate that due to strong hybridization between Al-2p and Ti-3d, there is a strong directional bonding between the Al and Ti atoms. Electronic structures reveal the underling mechanism of elastic properties and phonon focusing for Al₅Ti₂ and Al₁₁Ti₅.

• Periodical: Materials Science Forum (Volume 898)
• Pages: 1026-1035
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.898.1026
• Online since: June 2017
• Authors: Ping Ying Tang, Guo Hua Huang, Qing Lian Xie, Na Na Guan, Feng Ning*
• Keywords: Anisotropy, Elastic Properties, Electronic Structure, LPSs, Phonon Focusing

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