Abstract
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.
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