Crystal stability and the origin of transport properties of new MAX phases Y2AN (A = In, Tl): a theoretical background for experimental study

Crystal structure prediction has garnered considerable attention in recent years, and this study presents the density functional theory (DFT)-based first-principles prediction of the crystal stability and transport properties of Y2AN (A = In, Tl) MAX phase compounds for the first time. The calculated structural properties are consistent with other yttrium-containing M2AX phases. Most importantly, the formation enthalpy, cohesive energy, and predicted melting temperatures, combined with the total density of states (TDOS) analysis, indicate that Y2AN (A = In, Tl) phases are thermodynamically stable and exhibit good structural stability. These results provide a solid foundation for future research and practical applications. Additionally, phonon spectra show no imaginary modes along the high symmetry k-path, confirming dynamic stability. Our investigation also highlights the metallic nature of Y2AN (A = In, Tl) MAX phases, revealing that lower effective mass and higher Fermi velocity of electrons enhance their conductive properties, making them efficient in transporting charges and heat. Furthermore, in the ultraviolet (UV) region, both compounds exhibit their highest conductivity, highlighting their potentiality in UV-specific applications. The strong absorption also indicates them ideal candidates for the protective coatings against UV damage, and converting UV light into electrical signals. These findings would encourage further experimental validation and development, paving the way for innovative applications of these advanced materials.Graphical abstractThe electron effective masses for Y₂InN and Y₂TlN are nearly identical when calculated with the same exchange–correlation functionals, exhibiting notable isotropy. For the Y₂InN and Y₂TlN structures, the hole masses were computed along the α→β and λ→L directions, ranging from approximately 0.069 m₀ (LDA) to 0.086 m₀ (GGA-PBE) for Y₂InN, and from 0.069 m₀ (GGA-PBE) to 0.074 m₀ (LDA) for Y₂TlN. In the case of electron effective masses, the highest values were observed in the Γ→α direction, around 0.048 m₀ (GGA-PBE) for Y₂InN and approximately 0.038 m₀ (LDA) for Y₂TlN.