Structural stabilities, elastic property, and robust topological phases in Janus MoWCO2 MXene from first-principles investigation.

Two-dimensional (2D) topological materials have attracted considerable interest because of their potential applications in next-generation quantum and spintronic devices. In this work, we systematically investigate the structural, mechanical, and electronic properties of Janus MoWCO2 MXene using first-principles density functional theory (DFT) calculations, both with and without spin-orbit coupling (SOC). The energetically favored O-terminated configurations are examined in detail, revealing that the 2H phase exhibits higher thermodynamic, mechanical, and dynamical stability than the 1T phase. In the absence of SOC, both phases display metallic behavior. Upon inclusion of SOC, a band inversion emerges at the Γ point. In particular, SOC opens a narrow band gap of approximately 0.10 eV in the 2H phase, whereas the 1T phase remains gapless and exhibits semimetallic characteristics. Topological analysis based on helical edge states and Z2 invariants indicates that 2H-MoWCO2 is a strong topological insulator candidate, while 1T-MoWCO2 can be classified as a topological semimetal candidate. These findings suggest that Janus MoWCO2 MXene represents a promising two-dimensional platform for exploring SOC-driven topological phases and related quantum phenomena.