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

Abstract

By utilizing an evolutionary methodology on crystal structure search, we propose three new metastable phases for aluminum arsenide (AlAs) as follows: (1) a P6 4 22 symmetric structure 3 (hP6-AlAs), (2) a C222 symmetric structure (oC12-AlAs), and (3) a I3d symmetric structure 4 (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 9 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 0.468 eV and 1.356 eV, respectively. cI24-AlAs is a direct semiconductor with a gap value 1.761 eV.

III‐Nitride Polymorphs: XN (X=Al, Ga, In) in the Pnma Phase

“…Recently,m ore and more researchers have begun to study the polymorphs of the XN compounds (X = Al, Ga, In). [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Yang et al [6] investigated the structural, elastic,thermodynamic, electronic, and opticalp roperties of four novel compounds: Pmn2 1 -AlN, Pbam-AlN, Pbca-AlN, and Cmcm-AlN. They found that the AlN in the Cmcm phase has ab etter plasticity and also has al arger elastic anisotropyi nY oung's modulus than Pmn2 1 -AlN, Pbam-AlN, and Pbca-AlN.…”

“…They found that their hardness and Debye temperaturesb oth decrease with the X( X = N, P, As) atomic number,t hat is to say,f or wurtzite andz incblende, the hardnessand Debyet emperature are in the order of AlN > AlP > AlAs. Aq uasi-harmonic approximation was used to systematically evaluate the temperature dependence of thermodynamic properties for AlX (X = N, P, As) compounds.B yu tilizing an evolutionary methodology in ac rystal structure search, Liu et al [10] proposed three new metastable phases for AlAs, namely, hP6-AlAs, oC12-AlAs, and cI24-AlAs, the space groups being P6 4 22, C222, and I4 3d,r espectively.F rom electronic band-structure calculations, cI24-AlAs is ad irect semiconductor materialw ith ag ap value of 1.76 eV,w hereas oC12-and hP6-AlAs are indirect semiconductor materials with band gaps of 0.47 eV and 1.36 eV,respectively.…”

High-pressure induced phase transition of FeS2: Electronic, mechanical and thermoelectric properties

“…We performed global minimization of FeS 2 (at T = 0 K) by merging ab initio total energy calculations and the calypso technique on structural predictions, as implemented in the CALYPSO code [16][17][18]. The CALYPSO method has been successful to correctly predict HP structures for various systems [19][20][21][22][23]. The underlying ab initio electronic structure calculations and geometry relaxations were performed in the framework of density functional theory (DFT) using the Perdew−Burke−Ernzerhof (PBE) exchange−correlation functional [24] within GGA as implemented in the Vienna ab initio simulation package (VASP) code [25].…”

Physical Properties of XN (X = B, Al, Ga, In) in the Pm−3n phase: First-Principles Calculations

“…Therefore, in the application of semiconductors, compatibility means are often used to make the two compatible and utilize their respective advantages. Because of this, more and more attention has been paid to research on new structures and the physical properties of the compounds [1][2][3][4][5][6][7][8][9][10][11][12][13].…”