Centered Honeycomb NiSe2 Nanoribbons: Structure and Electronic Properties

Quasi-one-dimensional nanoribbons are excellent candidates for nanoelectronics and as electrocatalysts in hydrogen evolution reactions; therefore, we investigate by means of density functional theory the structure and electronic properties of a new kind of one-dimensional ribbons, namely, centered honeycomb NiSe2 nanoribbons. Depending on the crystallography and atomic composition of the edges, it is shown that these ribbons can belong to one of six zigzag or two armchair families. In the zigzag families, after edge reconstruction, all the bare ribbons are metallic. Hydrogen passivation produces band gaps in two of the six families by sweeping edge states, corresponding to the stablest nanoribbons. For the armchair nanoribbons, the geometrical reconstruction leads to semiconductors with small band gap, and the hydrogen passivation of the edges increases the band gap up to ∼0.6 eV. The inclusion of the spin–orbit interaction tends to reduce the band gaps, and the systems become metallic in the bulk limit. Several mechanisms are seen to determine band structure and stability: quantum confinement, edge states, density of broken bonds, and asymmetry with respect to the central line. As a result, some terminations are stable; others present edge reconstruction while SeH2 molecules are prone to desorb from the ribbon’s edges.