Comprehensive search for buckled honeycomb binary compounds based on noble metals (Cu, Ag, and Au)

Abstract: Honeycomb structure has been frequently observed in two-dimensional (2D) materials. CuAu in the buckled honeycomb (BHC) structure has been synthesized recently, which is the first case of 2D intermetallic compounds. Here, the dynamical stability of 2D $AX$ in the BHC structure, where $A=$ Cu, Ag, and Au and $X$ is a metallic element in the periodic table, is systematically studied by calculating phonon dispersions from first-principles. Among 135 $AX$, more than 50 $AX$ are identified to be dynamically stable. In addition, (i) a relationship between the dynamical stability and the formation energy, (ii) a correlation of dynamical stability between different constituents $A$, (iii) a trend of lattice parameters, and (iv) electronic and magnetic properties are discussed. Furthermore, a stable phase of B11-type AuZr is predicted based on both the result (ii) and the stability relationship between 2D and three-dimensional structures. The present findings stimulate future studies exploring physics and chemistry of 2D intermetallic compounds.