Abstract
First-principles calculations based on density functional theory (DFT) were employed to investigate systematically the structural, electronic, vibrational, elastic, and piezoelectric properties of monolayer Janus VBrSe in both 2H and 1T phases. Phonon dispersion analysis indicates dynamic instability of the 1Tphase at ambient conditions, as evidenced by the presence of imaginary frequencies, thereby excluding it from further consideration. Conversely, the 2Hphase is confirmed to be dynamically stable and energetically favorable, supporting its feasibility for experimental synthesis. The 2H-VBrSe exhibits a direct band gap, with its electronic structure demonstrating pronounced sensitivity to surface-induced strain effects, distinguishing it from conventional transition metal dichalcogenides (TMDs). Calculated Raman spectra provide characteristic vibrational modes enabling experimental phase identification. Notably, the 2H phase exhibits substantial out-of-plane piezoelectric coefficients, highlighting its potential for applications in energy harvesting and piezoelectric devices. These findings position 2H-VBrSe as a promising candidate for sensors, optoelectronic components, flexible electronics, and spintronic applications owing to its tunable band gap and strong piezoelectric response. This study offers critical insights into the phase stability and multifunctional properties of Janus VBrSe, laying the groundwork for its experimental realization and integration into next-generation technologies.