Computational exploration of 2D materials: From metal to MXene and XMene layers

Since the successful discovery and isolation of graphene in 2004, and the subsequent explosion and continuation of two-dimensional (2D) materials are undergoing and lasting until now. Although the layered semiconductors and heterostructures beyond graphene have in a stage of rapid growth. The metal or metallic layers are still in the stage of infancy. Here, we will provide an outlook for the applications of computational approaches to selected metallic 2D materials synthesis, properties and applications. Through electron beam irradiation, we synthesized a novel 2D Ti nanosheet using a suspension of Ti_0.91O₂ nanosheets. Density functional theory (DFT) calculations confirmed that this material is a non-magnetic superconductor with a moderate level of electron-phonon coupling and showing an excellent stability under strain and are prone to electronic topological transformations. In the realm of 2D metal carbides and borides, we introduced two innovative criteria to evaluate the potential for exfoliating MXenes from the 36 M₂AC MAX phases. Our analysis identified nine promising MAX phases, called Ti₂AlC, Ti₂GaC, Ti₂InC, Ti₂SnC, Ti₂TeC, V₂AlC, V₂GaC, V₂InC, and V₂SbC, suitable for exfoliation, with their stable MXenes (Ti₂C and V₂C) siblings. Expanding the exploration from MXenes into XMenes (anti- MXenes), the monolayer FeB with Pmma orthorhombic lattice was revealed to be a ferromagnetic metal with estimated critical temperature of 425 K, out-of-plane easy-axis and high magnetic anisotropic energy of 416.6 µeV/Fe. Further, this novel 2D FeB material holds promise in spin-polarized current injection. These recent discoveries of 2D metallic monolayers, spanning from 2D metals to MXenes and to XMenes, present excellent candidates for further experimental investigations, concurrently enabling advancements in quantum and spintronic device applications.

Keywords: Metallic 2D materials, Superconductor, Exfoliating, Ferromagnetic.

Jiawei Tang is a PhD candidate at Southeast University. His research focuses on the computational study of metallic and low-dimensional materials using first-principles calculations and machine learning. His current work explores the structural stability, electronic properties, and potential applications of two-dimensional (2D) systems.