The recently discovered phosphorenes are emerging as promising 2D materials for nanoelectronics. Novel structures and topologies can produce new properties and functionalities, and pave the way for potential new applications. For the first time, we predict two novel highly stable free-standing 2D monolayers of P and As with exotic hypercoordination motifs. This is the first hexacoordinate P and planar hexacoordinate As extended sheet. Ab initio calculations and molecular dynamics simulations demonstrate that these new Cu2X (X = P/As) materials are highly stable and are diamagnetic and metallic. Cu2P is slightly buckled without magnetism. For Cu2As, the exactly planar motif is the ground state. We observe an interesting phenomenon, i.e., buckling quenching of the magnetism in a 2D crystal. To our knowledge, this is the first example of buckling quenching of the magnetism in a 2D crystal. These results add a new dimension to the chemistry of phosphorus and arsenic.
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