Gentle tension stabilizes atomically thin metallenes

TL;DR

This study uses density-functional theory to analyze the stability of various atomically thin metallenes, revealing that tensile strain and low atomic density can enhance their dynamic stability, challenging traditional fixed-structure views.

Contribution

It introduces a new paradigm viewing crystalline metallenes as yielding membranes stabilized by tensile strain and low density, supported by comprehensive theoretical stability analysis.

Findings

128 out of 270 lattices are dynamically stable under tensile strain

Metallenes are often unstable at energy minima against amorphization

Tensile strain and low density improve metallene stability

Abstract

Metallenes are atomically thin two-dimensional (2D) materials lacking a layered structure in the bulk form. They can be stabilized by nanoscale constrictions like pores in 2D covalent templates, but the isotropic metallic bonding makes stabilization difficult. A few metallenes have been stabilized but comparison with theory predictions has not always been clear. Here, we use density-functional theory calculations to explore the energetics and dynamic stabilities of $45$ metallenes at six lattices (honeycomb, square, hexagonal, and their buckled counterparts) and varying atomic densities. We found that of the $270$ different crystalline lattices, 128 were dynamically stable at sporadic densities, mostly under tensile strain. At the energy minima, lattices were often dynamically unstable against amorphization and the breaking down of metallene planarity. Consequently, the results imply that crystalline metallenes should be seen through a novel paradigm: they should be considered not as membranes with fixed structures and lattice constants but as yielding membranes that can be stabilized better under tensile strain and low atomic density. Following this paradigm, we rank the most promising metallenes for 2D stability and hope that the paradigm will help develop new strategies to synthesize larger and more stable metallene samples for plasmonic, optical, and catalytic applications.