Density functional theory computations were performed to investigate the stabilities and magnetic and electronic properties of VSe 2 bulk, few-layers, monolayer, and its derived nanoribbons (NRs) and nanotubes in both T and H phases. All these materials are ferromagnetic, but exhibit versatile electronic properties. The VSe 2 bulk and few-layers in either T or H phase, and T monolayer are metallic, while the H monolayer is a semiconductor. For nanoribbons, the zigzag NRs in both T and H phases and the armchair NRs in T phase are metallic, while the armchair NRs in H phase are halfmetallic. The edge hydrogenation can retain or amend the electronic property of the pristine NRs depending on the chirality and phases. Regardless of the chirality, nanotubes in T phase are half-metallic, while those in H phase are metals. These findings provide a simple and effective route to tune the electronic properties of VSe 2 nanostructures in a wide range and also facilitate the design of VSe 2 -based nanodevices.
Inspired by the recent theoretical finding that penta-graphene, composed entirely of carbon pentagons, is dynamically and mechanically stable [Proc. Natl. Acad. Sci. U. S. A., 2015, 112, 2372-2377], we computationally designed a new two-dimensional (2D) inorganic material, a pentagonal B2C monolayer (penta-B2C), in which each pentagon contains three boron and two carbon atoms, the C atom is four-coordinated with four B atoms, and all the B atoms are three-coordinated with two C atoms and one B atom, forming a buckled 2D network. The pentagonal B2C monolayer is semiconducting with a wide indirect band gap of 2.28 eV from HSE calculations. The absence of imaginary modes in its phonon spectrum, and the high melting point predicted by molecular dynamics (MD) simulations indicate its good stability. Interestingly, the buckled structure could be stretched to planar under 15% biaxial tensile strain, and the band gap will be strikingly reduced to 0.06 eV. The semiconducting properties of penta-B2C could also be switched to those of a metallic semiconductor under certain biaxial strains, while uniaxial strains could only tune the band gaps without changing the semiconducting characteristics.
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