Recently, borophene was reported to be produced on the silver surfaces. 1 We employ density functional theory and electronic transport calculations to investigate the stabilities, electronic structures and transport properties of borophene nanoribbons. The stability of borophene nanoribbon increases with its width and only the lined-edged borophene nanoribbons are stable in the free-standing form. Such anistropic stabilty dependence is ascribed to the large scale delocalization of π electrons along the boron rows. Particularly, all line-edge borophene nanoribbons undergo edge reconstructions, in which the out-of-plane bulking edge atoms are reconstructed to form quasi planar edge structures. Such edge reconstructions have not yet reported, which is critical for the formation of boron nanostrcutrues. Subsequent electronic transport calculations based on non-equilibium Green's function indicate that the line-edge borophene nanoribbons exhibit low-resistivity Ohmic conductance. Our results indicate that the line-edge borophene nanoribbons present remarkable properties (high thermal stabilities, Ohmic contance with low electrical resistivity and good rigidities) and are promising for applications as one-dimensional electrical connections in compact nanoscale circuits.

We investigate the spin-dependent electric and thermoelectric properties of ferromagnetic zigzag α-graphyne nanoribbons (ZαGNRs) using density-functional theory combined with non-equilibrium Green's function method. A giant magnetoresistance is obtained in the pristine even-width ZαGNRs and can be as high as 10(6)%. However, for the doped systems, a large magnetoresistance behavior may appear in the odd-width ZαGNRs rather than the even-width ones. This suggests that the magnetoresistance can be manipulated in a wide range by the dopants on the edges of ZαGNRs. Another interesting phenomenon is that in the B- and N-doped even-width ZαGNRs the spin Seebeck coefficient is always larger than the charge Seebeck coefficient, and a pure-spin-current thermospin device can be achieved at specific temperatures.

Inorganic halide perovskites CsPbX3 (X = Cl, Br, I) with excellent thermal stability are widely drawing increasing attention from researchers in light-emitting diodes and solar cells. The band gap and dielectric constant are two important parameters to characterize the optoelectronic performance in semiconductors. To map the underlying relationship between the dielectric constant and band gap for mixed-halide perovskites, atomic and electronic properties including mixing enthalpy, band gap, and dielectric constant in different halogen concentrations, substitution sites, and dimensions are investigated systematically using density functional theory. The results demonstrate that both dimensionality and halide composition have a small influence on mixing enthalpy, and structures with different halogen concentrations are prone to form at room temperature in bulk and monolayer perovskites. The increase in the band bowing parameter is 0.004–0.196 eV in the case of tuning the composition, while the increased value is 0.440–0.549 eV by increasing the dimensionality from monolayer to bulk counterpart, suggesting that the method of controlling dimensions has more influence on their band bowing than halide composition. Furthermore, we obtained an apparent positive linear correlation between the dielectric constant and 1/E g 2, which can be useful to deeply understand the dielectric properties of all dimensionalities. Our work provides a theoretical basis for different dimensionality and composition perovskite materials with potential applications in optoelectronic devices.

We study the crystal reconstruction in the presence of monovacancies (MVs), divacancies (DVs) and linear vacancies (LVs) in a zigzag silicene nanoribbon (ZSiNR) with transversal symmetry. Their influence on the electric and thermoelectric properties is assessed by the density functional theory combined with the nonequilibrium Green's functions. In particular, we focus on the spin resolved conductance, magnetoresistance and current-voltage curves. A 5-atom-ring is formed in MVs, a 5-8-5 ring structure in DVs, and a 8-4-8-4 ring structure in LVs. The linear conductance becomes strongly spin dependent when the transversal symmetry is broken by vacancies especially if they are located on the ribbon's edges. The giant magnetoresistance can be smeared by asymmetric vacancies. Single spin negative differential resistance may appear in the presence of LVs and asymmetric MVs or DVs. A strong spin Seebeck effect is expected at room temperature in ZSiNRs with LVs.