First-principles study of novel honeycomb-shaped 2D oxygen crystal on an ultraflat Cu (111)

Two-dimensional (2D) materials have been central to the discovery of novel phenomena and applications due to their unique properties derived from reduced dimensionality. We present the discovery of a novel 2D oxygen crystal isomorphic to graphene, termed “oxylene” on an ultraflat Cu (111) surface in a 4x4 periodicity confirmed by scanning tunneling microscopy (STM) & density functional theory (DFT) studies. Our first-principles total-energy calculations based on DFT, utilizing the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) for exchange-correlation energy and the projected augmented wave (PAW) method, further elucidate the electronic and magnetic properties of oxylene. This structure exhibits unique magnetization densities at the face-centered cubic (fcc) and hexagonal closed-packed (hcp) sites, with magnetic octupole moments attributed to oxygen atoms, and supports various linear responses, such as magneto-optical Kerr and piezoelectric effects. The unique electronic and magnetic properties, along with its high surface area and reactivity make oxylene a promising candidate for applications in catalysis and spintronic devices.