Structural, anisotropic elasticity, and thermal properties of Ga2O3 polymorphs: A first-principles study

The anisotropic elastic and thermal properties of five different Ga₂O₃ polymorphs were examined through first-principles calculations grounded in density functional theory (DFT). All phases satisfy mechanical and dynamical stability criteria and exhibit ductile characteristics. Based on the derived elastic constants C_ij, the elastic moduli (B, E, G and v) and hardness parameters (H_V, K_IC and M_dt) for these polymorphs were computed. Anisotropy indices and three-dimensional surface plots of elastic moduli quantify directional stiffness variations, revealing the elastic anisotropy ranking γ > β > ε > δ > α. Acoustic properties derived from Debye temperature, Grüneisen parameter, and direction-dependent sound velocities construct a comprehensive anisotropic sound-velocity database. Lattice thermal conductivities predicted by Slack and Callaway models demonstrate that α- Ga₂O₃ attains the highest thermal conductivity at and above its Debye temperature, while β- Ga₂O₃ leads at lower temperatures. These findings furnish design guidelines for selecting optimal Ga₂O₃ polymorphs in high-temperature power electronics, surface-acoustic-wave devices, and thermal-management applications.