Elastic Stability and Multifunctional Properties of Wurtzite Aluminum Nitride from First Principles

Elastic stability is a critical requirement for piezoelectric materials intended for reliable energy-harvesting operation under cyclic mechanical and thermal loading. In this work, we present a convergence-verified first-principles density-functional theory (DFT) investigation of the elastic stability and multifunctional properties of wurtzite aluminum nitride (AlN). Structural optimization yields equilibrium lattice parameters of a = 3.111 ？ and c = 4.978 ？. The calculated elastic constants satisfy all Born stability criteria for hexagonal crystals, confirming the mechanical stability of wurtzite AlN. Voigt-Reuss-Hill averaging reveals high bulk, shear and Young’s moduli together with pronounced elastic anisotropy. The calculated elastic moduli indicate a stiff material with brittle mechanical character. Electronic band-structure and density-of-states analyses confirm a wide direct Γ-Γ band gap, consistent with ultra-wide-band-gap nitride behavior and high electrical insulation. Thermoelectric transport trends, evaluated within the constant relaxation time approximation, show moderate Seebeck coefficients but very low electrical conductivity and high lattice thermal conductivity, resulting in poor intrinsic thermoelectric efficiency. These results establish a consistent theoretical benchmark linking elastic stability, electronic structure and transport behavior in wurtzite AlN and clarify its suitability as a robust, lead-free material platform for piezoelectric energy-harvesting applications.