First-Principles Study of Li۲AgAl: A Density Functional Theory Approach

Heusler alloys are intermetallic compounds with well‑ordered crystal structures that have attracted considerable attention due to their diverse electronic behavior and potential technological applications. Among them, inverse Heusler compounds have emerged as promising materials for advanced electronic and optoelectronic devices. In this work, the structural, mechanical, electronic, optical, and dynamical properties of the inverse Heusler compound Li۲AgAl were investigated using density functional theory (DFT). The calculations were carried out using the Quantum ESPRESSO package within a plane‑wave basis set and ultrasoft pseudopotentials. The exchange–correlation interaction was described using the generalized gradient approximation in the Perdew–Burke–Ernzerhof (GGA‑PBE) scheme, while the HSE۰۶ hybrid functional was employed to obtain more accurate electronic and optical results. In addition, lattice dynamical properties were analyzed through phonon dispersion relations and phonon density of states using the Phonopy package. The phonon spectrum confirms the dynamical stability of Li۲AgAl, as no imaginary frequencies appear across the Brillouin zone. A clear phonon gap between acoustic and optical branches is also observed, originating from the mass difference between constituent atoms and variations in bonding strength. This feature suppresses phonon–phonon scattering and leads to reduced lattice thermal conductivity. Electronic band structure calculations reveal the metallic nature of Li۲AgAl, while optical analysis indicates strong absorption in the ultraviolet region. Overall, these results provide valuable insight into the physical characteristics of Li۲AgAl and highlight its potential for future electronic, optoelectronic, and thermoelectric applications.

کلیدواژه ها:

Inverse Heusler compound ، Density Functional Theory (DFT) ، Quantum ESPRESSO