DFT investigation of the electronic band structure of 2D Janus HfSTe in the 1T phase

Two-dimensional transition metal dichalcogenides (2D TMDs) have emerged as promising materials for next-generation technologies due to their versatile physical properties. Among them, Janus TMDs represent a unique class with broken structural symmetry, which induces an out-of-plane dipole moment and enables novel functionalities. In this work, we investigate the structural, vibrational, and electronic properties of a newly proposed Janus HfSTe monolayer in the centered honeycomb (1T) phase. Two configurations are examined, namely, the heterolayer and the alternating forms. The phonon dispersion confirms the dynamical stability, and the density of states is systematically analyzed. Electronic structure calculations using both B3LYP and GGA-PBE functionals consistently indicate metallic behavior, demonstrating that the electronic nature is robust against the choice of exchange–correlation functional. Cohesive energy calculations reveal strong bonding, with the alternating structure being more stable by 0.23 eV/atom. Charge density difference plots visualize the asymmetric charge transfer characteristic of Janus materials, while work function calculations show a significant difference (1.1–1.3 eV) between the S- and Te-terminated surfaces. Ab initio molecular dynamics simulations confirm thermal stability at room temperature. The intrinsic metallicity of 2D HfSTe, combined with its Janus-induced surface asymmetry, highlights its potential for applications in electronics, energy storage, catalysis, and related technologies. • DFT study of a novel 2D Janus 1T-HfSTe monolayer. • Phonon and AIMD confirm dynamical and thermal stability at 300 K. • Both phases show robust intrinsic metallic behavior with PBE and B3LYP. • Alternating phase is energetically favored by 0.23 eV/atom over heterolayer. • Janus asymmetry yields a 0.4–0.6 eV surface work-function difference.