Expanding the Structural and Compositional Space of Two-Dimensional M₂X₂T_<i>y</i> Materials via Simulated Etching of Layered YM₂X₂ Phases

Inspired by the recent synthesis of 2D Ru2SixOy, obtained by selective removal of Y from the 3D parent phase YRu2Si2, we simulate the selective etching process of the family of laminates YM2X2, with M being a 3d, 4d, or 5d transition metal and X = Al, Ga, In, Si, Ge, Sn, P, As, Sb, S, Se, or Te. We assess the thermodynamic stability of 300 3D YM2X2 compounds through the formation enthalpy with respect to competing phases, ΔHcp, where ΔHcp < 0(20) meV/atom predicts a phase as thermodynamically stable (close to stable). 3D phases predicted as stable are assessed computationally for selective etching of Y in acidic media, resulting in ideal 2D units M2X2Ty, where O and F are considered as terminating species T. We predict 17 2D structures, out of which 11 are not previously reported. All of these are identified as dynamically stable and are predicted to be possible to synthesize through selective etching of parent 3D compounds. All are found to be either metals or semimetals, with further tuning potential being possible by alteration of surface terminations.