A theoretical insight into phonon heat transport in graphene/biphenylene superlattice nanoribbons: a molecular dynamic study

Thermal rectification in novel two-dimensional hybrid graphene/BCN sheets: A molecular dynamics simulation

The graphene-like monolayer of carbon, boron and nitrogen that maintains the native hexagonal atomic lattice (BCN), is a novel semiconductor with special thermal properties. Herein, with the aid of a non-equilibrium molecular dynamics approach (NEMD), we study phonon thermal rectification in a hybrid system of pure graphene and BCN (G-BCN) in various configurations under a series of positive and negative temperature gradients. We begin by investigating the relation of thermal rectification to sample's mean temperature, T, and the imposed temperature difference, ΔT, between the two heat baths at its ends. We then move to explore the effect of varying strain levels of our sample on thermal rectification, followed by Kapitza resistance calculations at the G-BCN interface, which shed light on the interface effects on thermal rectification. Our simulation results reveal a BCN-configuration-dependent behavior of thermal rectification. Finally, the underlying mechanism leading to a preferred direction for phonons is studied using phonon density of states (DOS) on both sides of the G-BCN interface.

Controlling the Thermal Conductivity of Monolayer Graphene with Kirigami Structure

In this work, the thermal conductivity performance of graphene kirigami (GK) was systematically investigated via molecular dynamics (MD) simulations. The results indicate that the degree of defects (DD) on GK has a significant influence on thermal conductivity. Reducing the DD is the most effective way to decrease the thermal conductivity of GK. For zigzag-incised GK sheets, the change rate of thermal conductivity can reach up to 1.86 W/mK per 1% change in DD by tuning the incision length. The rate of changing thermal conductivity with DD can be slowed down by changing the width among incisions. Compared with the zigzag-incised GK sheets, heat transfer across the armchair-incised GK comes out more evenly, without significant steep and gentle stages along the heat transfer routes. More importantly, the GK structure can adjust the thermal conductivity by stretching, which the previously reported nanoporous graphene does not have. The change rate of thermal conductivity achieves about 0.17 W/mK with 1% stretching strain for simulated GK and can be further reduced at high tensile strain rates, benefiting the precise and variable control of the thermal conductivity of the monolayer graphene.

A Theoretical Investigation on the Physical Properties of Zirconium Trichalcogenides, ZrS3, ZrSe3 and ZrTe3 Monolayers

In a recent advance, zirconium triselenide (ZrSe3) nanosheets with anisotropic and strain-tunable excitonic response were experimentally fabricated. Motivated by the aforementioned progress, we conduct first-principle calculations to explore the structural, dynamic, Raman response, electronic, single-layer exfoliation energies, and mechanical features of the ZrX3 (X = S, Se, Te) monolayers. Acquired phonon dispersion relations reveal the dynamical stability of the ZrX3 (X = S, Se, Te) monolayers. In order to isolate single-layer crystals from bulk counterparts, exfoliation energies of 0.32, 0.37, and 0.4 J/m2 are predicted for the isolation of ZrS3, ZrSe3, and ZrTe3 monolayers, which are comparable to those of graphene. ZrS3 and ZrSe3 monolayers are found to be indirect gap semiconductors, with HSE06 band gaps of 1.93 and 1.01 eV, whereas the ZrTe3 monolayer yields a metallic character. It is shown that the ZrX3 nanosheets are relatively strong, but with highly anisotropic mechanical responses. This work provides a useful vision concerning the critical physical properties of ZrX3 (X = S, Se, Te) nanosheets.