Physical Properties of Hf‐Based MXenes Monolayers for Optoelectronic and Clean Energy

In this work, the structural, dynamical, electronic, optical, and thermodynamic properties of Hf ₂ CCl ₂ and Hf ₂ CBr ₂ MXene monolayers were investigated using density functional theory, the HSE06 hybrid functional, and ab initio molecular dynamics (AIMD) simulations. Phonon dispersion calculations together with AIMD simulations at 300 K confirm the dynamical and thermal stability of both monolayers. The optimized structures exhibit lattice constants of 3.411 and 3.479 Å and cohesive energies of −6.830 and −6.513 eV/atom for Hf ₂ CCl ₂ and Hf ₂ CBr ₂ , respectively. Electronic structure calculations indicate that both compounds are direct‐bandgap semiconductors with HSE06 bandgaps of 0.82 and 0.79 eV. These values correspond to the near‐infrared spectral region, making the two monolayers relevant for infrared optoelectronic applications. The calculated electron and hole effective masses are relatively small, suggesting favorable charge‐transport characteristics. In addition, both materials exhibit strong optical absorption, reaching values on the order of 10 ⁵  cm ⁻¹ in the UV–visible region. Thermodynamic analysis further shows that the two systems remain stable over a wide temperature range up to 1000 K. Overall, these results highlight the potential of Hf ₂ CCl ₂ and Hf ₂ CBr ₂ monolayers for applications in optoelectronic and energy‐conversion technologies.