In depth first-principles investigation of phase stability, structural, vibrational, electronic, elastic, piezoelectric, and magnetic properties in vanadium-based janus dichalcogenide monolayer VBrSe.

Abstract

Context: This study presents a comprehensive first-principles investigation of the structural, electronic, vibrational, elastic, and piezoelectric properties of monolayer Janus VBrSe in both 2H and 1 T phases. The 1 T phase is found to be dynamically unstable, whereas the 2H-VBrSe phase is confirmed to be both energetically favorable and dynamically stable, indicating its feasibility for experimental synthesis. The 2H phase exhibits a direct band gap with pronounced strain sensitivity, significant out-of-plane piezoelectric response, and distinct Raman-active vibrational modes, facilitating phase identification. Micromagnetic simulations further reveal robust ferromagnetic ordering. These properties establish 2H-VBrSe as a multifunctional material suitable for next-generation applications in sensors, optoelectronics, flexible devices, and spintronic systems.

Methods: Density functional theory (DFT) calculations were performed using the VASP package, incorporating spin-orbit coupling and van der Waals corrections to accurately capture the behavior of layered systems. Electronic structure and geometry were optimized using advanced exchange-correlation functionals to improve band gap accuracy. Phonon dispersion analyses confirmed dynamic stability, while elastic constants and piezoelectric coefficients were computed to assess mechanical and electromechanical performance. Ferromagnetic behavior was evaluated via micromagnetic simulations using MuMax3. The theoretical framework enables further exploration of temperature-dependent phenomena, such as thermal stability and dynamical response, through ab initio molecular dynamics.