Transition Metal Atoms Absorbed Bare Graphene-like Carbon Nitride Nanoribbons:A DFT+U Study

Monolayer graphene-like carbon nitride (g-CN), a new 2D nanomaterial, have been obtained in experiment, which has a honeycomb-like structure similar to graphene and the conduction band minimum (CBM) of g-CN is also contributed by antibonding C/N-pz π* state. While unlike graphene, g-CN has two inquivalent membered carbon-nitride rings in its unit. Thus g-CN possesses extra paired electrons, originating from C-N bond, which will contribute the valence band maximum (VBM) So g-CN is expected to be found specially attractive properties for the application of nanoelectronic devices. The bare zigzag g-CN nanoribbons with hydro gen-pas sivated edges (Zg-CNNRs) is nonmagnetic and semiconducting.It has not own any intrinsic spin ploarization, which make it ineffective for the spintronic applications. Under this situation, it is necessary to induced spin moment in them. One easy way could be the incopotation of spin-ploarized transition metal atoms(TM), which has been widely used in other similar systems. Moreover previous research have shown that graphitic carbon nitride sheet (g-C3N4), similar to graphene-like carbon nitride (g-CN)sheet in structure, with smaller cavities than g-CN can trap TM atoms regularly in its sheet and effectually modified the electronic, magnetic and optical properties. As we know, there are big cavities in g-CN, particularly we believe that make it more favor in capturing atoms. Motivated by these findings, we examine the adsorption process of TM (Sc, Ti, V, Cr, Mn) on the bare zigzag edge g-CN in this paper.Our study have been explored under the density functional theory (DFT) with local Coulomb interactions (U). In our calculation, the TMs lying on the cavity of Zg-CNNRs show the energetically most stable structure. Under the most stable structures of TM@Zg-CNNRs, we systematically investigate their structural, electronic and magnetic properties. Though the change of structure of TM@Zg-CNRs with Jahn-Teller distortion take place inevitably, it keep still planar. Our results show that bare Zg-CNNRs with nonmagnetic semiconductor become magnetic met al. The hybridize between TMs d-orbitals and Zg-CNNRs p-orbitals should be responsible for the change of electromagnetism property due to adsorption. Moreover,we discuss the magnetic coupling between 3d-TMs absorbed in Zg-CNNRs. We consider two TMs embedded in one and two neighboring cavities for comparison. Our results show that the transition atoms are uniformly and separately distributed without forming any cluster.For the case of two neighboring cavities, unlike the cases of TM@g-CN, it is found that Sc,Ti, V, Cr and Mn exhibit AFM coupling. For the case of one cavity, the magnetic moments of the adsorbed atoms are larger than that of theTM@g-CN. These effects should be responsible for the quantum size effect.