Stability and physical property modulation in Ag/Cu-alloyed Au monolayers with triangular lattices: A first-principles investigation

Abstract

Comprehensive first-principles calculations were performed to investigate how Ag and Cu alloying modulates the structural, energetic, and electronic properties of two-dimensional Au monolayers, resulting in the formation of AuAg and AuCu alloys. Both alloyed systems are thermodynamically stable and adopt an isosceles triangular lattice structure. The bond lengths in the alloyed monolayers generally fall between those of their elemental counterparts, with AuCu exhibiting notably shorter Au–Cu bonds, reflecting stronger atomic interactions.

Importantly, the binding energy of the AuCu monolayer is more negative than that of both pure Au and pure Cu monolayers, indicating enhanced stability due to cooperative bonding effects and orbital hybridization. Ab initio molecular dynamics (AIMD) simulations confirm thermal stability up to ∼1000 K, beyond which structural degradation occurs. Phonon dispersion calculations reveal no imaginary frequencies, supporting the dynamic stability of both alloyed systems.

Electronic band structure and density of states (DOS) analyses confirm their metallic character, with stronger hybridization observed in AuCu due to its reduced bond length and compact structure. Mechanical property evaluations—including elastic constants, Young’s modulus, and Poisson’s ratio—demonstrate that alloying leads to a reduction in stiffness and an increase in anisotropy. These findings highlight the tunability of 2D noble metal monolayers via alloying, offering promising avenues for future applications in flexible electronics, catalysis, and nanoscale devices.