High-pressure phases of AlxIn1−xN compounds: First principles calculations

- Identification of novel high pressure AlxIn1−xN phases through evolutionary algorithm.
- All metastable Al-In-N compounds possess sufficient dynamical stability.
- Physical properties of pressure induced AlxIn1−xN were measured via ab initio calculations.
- Composition effect on brittleness, Debye temperature and anisotropy are reported.
- Thermodynamic evaluation was carried out.

Novel high pressure metastable phases within Al-In-N system have been comprehensively explored via evolutionary algorithm USPEX, under both variable and fixed composition schemes. At 2.5 GPa, only Al7In2N9 (Cm) and Al2In2N4(I4¯2d) are identified. Candidate structures at 5.0 GPa expand to orthorhombic Al4In2N6(Cmc21), two tetragonal Al2In2N4(I4¯2d) plus AlIN4N5(I4¯) and trigonal AlIn5N6(R3). Increasing the pressure beyond 5.0 GPa appears to upset the stability of AlxIn1-xN. Using ab initio calculations based on systematic density functional theory, we also outline the electronic, lattice, mechanical and thermodynamic properties of these phases. Band structure, PDOS and Bader analyses show that these alloys are direct band gap semiconductor with certain degree of covalent nature in an ionic bonding. Corrected energy gap ranges from 0.771 eV to 4.995 eV. Mechanical and dynamical stabilities of abovementioned alloys are further revealed by the computations of independent elastic parameters and phonon dispersion curves. All the studied species demonstrate considerable elastic anisotropy and moderate hardness. Their simulated Vickers hardness ranges between 13.3 GPa and 21.6 GPa. Through quasi harmonic Debye model, composition dependence of thermal influenced macroscopic properties is quantitatively analyzed as well.

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