Graphenylene nanoribbons: electronic, optical and thermoelectric properties from first-principles calculations

Enhancement of thermoelectric performance in graphenylene nanoribbons by suppressing phonon thermal conductance: the role of phonon local resonance

Based on the method of non-equilibrium Green's function, we investigate the thermal transport and thermoelectric properties of graphenylene nanoribbons (GRNRs) with different width and chirality. The results show that the thermoelectric (TE) performance of GRNRs significantly increases with decreasing ribbon width, which stems from the reduction of thermal conductance. In addition, by changing the ribbon width and chirality, the figure of merit (ZT) can be controllably manipulated and maximized up to 0.45 at room temperature. Moreover, it is found that theZTvalue of GRNRs with branched structure can reach 1.8 at 300 K and 3.4 at 800 K owing to the phonon local resonance. Our findings here are of great importance for thermoelectric applications of GRNRs.

Modelling of Electron and Thermal Transport in Quasi-Fractal Carbon Nitride Nanoribbons

In this work, using calculations based on the density functional theory, molecular dynamics, non-equilibrium Green functions method, and Monte Carlo simulation, we study electronic and phonon transport in a device based on quasi-fractal carbon nitride nanoribbons with Sierpinski triangle blocks. Modifications of electronic and thermal conductance with increase in generation g of quasi-fractal segments are estimated. Introducing energetic disorder, we study hopping electron transport in the quasi-fractal nanoribbons by Monte Carlo simulation of a biased random walk with generalized Miller–Abrahams transfer rates. Calculated time dependencies of the mean square displacement bear evidence of transient anomalous diffusion. Variations of anomalous drift-diffusion parameters with localization radius, temperature, electric field intensity, and energy disorder level are estimated. The hopping in quasi-fractal nanoribbons can serve as an explicit physical implementation of the generalized comb model.

Influences of hole/electron-lattice coupling on phase transition between λ-Ti3O5and β-Ti3O5

The phase transition between λ-Ti3O5and β-Ti3O5is an intriguing process that can be driven in multiple ways. However, the phase transition has not been reasonably and universally analyzed in atomic-scale, because it is limited by experimental inaccessibility. Here, the nudged elastic band method, crystal orbital Hamiltonian population integral calculation, phonon calculation, and electron (or hole) doping calculation are used to investigate the phase transition between λ-Ti3O5and β-Ti3O5. The atomic displacement mode in the phase transition between the β-Ti3O5and λ-Ti3O5is provided, and a theory that the coupling between the lattice and excited electrons (or holes) is responsible for the phase transition between λ-Ti3O5and β-Ti3O5is established.

AA-Stacked Borophene-Graphene Bilayer with Covalent Bonding: Ab Initio Investigation of Structural, Electronic and Elastic properties

In this Letter, we study the structural, electronic, and elastic properties of single-layer striped borophene stacked on top of single-layer graphene. Through DFT calculation, we show that both the properties of striped borophene and graphene are not fully preserved in the novel heterostructure, which obviously depends on the nature of the chemical bond between the layers. The obtained phonon spectrum confirms the stability of this compound. The divergence of branches in the band structure appears below the Fermi level in the K point in the first Brillouin zone. Moreover, this heterostructure possesses excellent elastic properties and can be considered for use in the field of 2D acousto- and optoelectronics.