Metastable phases, phase transformation and properties of AlAs based on first-principle study

• Published in: Computational materials science Vol. 128; pp. 337 - 342
• Main Authors: Liu, Chao, Ma, Mengdong, Yuan, Xiaohong, Sun, Hao, Ying, Pan, Xu, Bo, Zhao, Zhisheng, He, Julong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2017
• Subjects: Aluminum arsenide; Electronic property; Electronics; Energy gaps (solid state); First-principle; Mathematical analysis; Mechanical property; Metastable phases; Phase transformation; Phase transformations; Searching; Semiconductors; Symmetry; Electronic property; Phase transformation; Aluminum arsenide; First-principle; Mechanical property
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2016.11.052

Utilizing CALYPSO, three new metastable phases for AlAs are proposed: (1) a P6422 symmetric structure (hP6-AlAs), (2) a C222 symmetric structure (oC12-AlAs), and (3) a I4¯3d symmetric structure (cI24-AlAs). With controlling unloading pressure rate, oC12-, hP6-, and cI24-AlAs may be acquired by quenching NiAs- or cmcm-AlAs. oC12-, and hP6-AlAs possess similar hardness, which is higher than that of cI24-AlAs. Meanwhile, oC12-, and hP6-AlAs hold similar shear anisotropic factors, which are smaller than that of cI24-AlAs. Electronic band structure calculation reveals that at zero pressure, oC12-AlAs and hP6-AlAs possess indirect band gaps of 0.468eV and 1.356eV, respectively. cI24-AlAs is a direct semiconductor with a gap value 1.761eV. [Display omitted] By utilizing an evolutionary methodology on crystal structure search, we propose three new metastable phases for aluminum arsenide (AlAs) as follows: (1) a P6422 symmetric structure (hP6-AlAs), (2) a C222 symmetric structure (oC12-AlAs), and (3) a I4¯3d symmetric structure (cI24-AlAs). By controlling the unloading pressure rate, oC12-, hP6-, and cI24-AlAs may be acquired through quenching NiAs-AlAs. The elastic constants and phonon dispersion spectra are calculated to certify the mechanical and dynamic stabilities of three newly discovered phases. On the basis of first-principle study, we explore phase transformations under pressure for several AlAs polymorphs. The calculation of mechanical properties illustrates that oC12-, and hP6-AlAs possess similar hardness levels, which are higher than that of cI24-AlAs. Meanwhile, oC12-, and hP6-AlAs hold similar shear anisotropic factors, which are smaller than that of cI24-AlAs. Electronic band structure calculation reveals that at zero pressure, oC12-, and hP6-AlAs possess indirect band gaps of 0.468eV and 1.356eV, respectively. cI24-AlAs is a direct semiconductor with a gap value 1.761eV.