A novel oxidized hierarchical porous carbon with vesicule-like ultrathin graphitic walls for efficient removal of anionic and cationic dyes.

This work developed a novel oxidized hierarchical porous carbon (OHPC) with vesicule-like ultrathin graphitic walls via a method of air oxidation and used as an efficient adsorbent for Congo red (CR) and Malachite green (MG) removal. Results show that the OHPC2 oxidized at 400 °C possesses three-dimensional hierarchical pores with vesicule-like ultrathin graphitic walls. The prepared OHPC2 not only has a large specific surface area of 1020 m g with a high pore volume, but also has abundant oxygen-containing functional groups.

General-purpose machine-learned potential for 16 elemental metals and their alloys.

Machine-learned potentials (MLPs) have exhibited remarkable accuracy, yet the lack of general-purpose MLPs for a broad spectrum of elements and their alloys limits their applicability. Here, we present a promising approach for constructing a unified general-purpose MLP for numerous elements, demonstrated through a model (UNEP-v1) for 16 elemental metals and their alloys. To achieve a complete representation of the chemical space, we show, via principal component analysis and diverse test datasets, that employing one-component and two-component systems suffices.

Combining linear-scaling quantum transport and machine-learning molecular dynamics to study thermal and electronic transports in complex materials.

We propose an efficient approach for simultaneous prediction of thermal and electronic transport properties in complex materials. Firstly, a highly efficient machine-learned neuroevolution potential (NEP) is trained using reference data from quantum-mechanical density-functional theory calculations. This trained potential is then applied in large-scale molecular dynamics simulations, enabling the generation of realistic structures and accurate characterization of thermal transport properties.

Curvature and van der Waals interface effects on thermal transport in carbon nanotube bundles.

A van der Waals (vdW) heterostructure, can be used in efficient heat management, due to its promising anisotropic thermal transport feature, with high heat conductance in one direction and low conductance in the rest. A carbon nanotube (CNT) bundle, can be used as one of the most feasible vdW heterostructures in a wide range of nanoscale devices. However, detailed investigations of heat transport in CNT bundles are still lacking.

Engineering Thermal Transport across Layered Graphene-MoS Superlattices.

Layering two-dimensional van der Waals materials provides a high degree of control over atomic placement, which could enable tailoring of vibrational spectra and heat flow at the sub-nanometer scale. Here, using spatially resolved ultrafast thermoreflectance and spectroscopy, we uncover the design rules governing cross-plane heat transport in superlattices assembled from monolayers of graphene (G) and MoS (M). Using a combinatorial experimental approach, we probe nine different stacking sequences, G, GG, MG, GGG, GMG, GGMG, GMGG, GMMG, and GMGMG, and identify the effects of vibrational mismatch, interlayer adhesion, and junction asymmetry on thermal transport.

Solid Solution YbCaCdSb: Structure, Thermoelectric Properties, and Quality Factor.

Solid solutions of YbACdSb (A = Ca, Sr, Eu; ≤ 1) are of interest for their promising thermoelectric (TE) properties. Of these solid solutions, YbCaCdSb has end members with different crystal structures. YbCdSb crystallizes in the polar space group 2, whereas CaCdSb crystallizes in the centrosymmetric space group .

Short-Range Order in GeSn Alloy.

Group IV alloys have been long viewed as homogeneous random solid solutions since perceiving them as Si-compatible, direct-band gap semiconductors 30 years ago. Such a perception underlies the understanding, interpretation, and prediction of alloys' properties. However, as the race to create scalable and tunable device materials enters a composition domain far beyond the alloys' equilibrium solubility, a fundamental question emerges as to how random these alloys truly are.

Mn-intercalated MoSe under pressure: Electronic structure and vibrational characterization of a dilute magnetic semiconductor.

Intercalation offers a promising way to alter the physical properties of two-dimensional (2D) layered materials. Here, we investigate the electronic and vibrational properties of 2D layered MoSe intercalated with atomic manganese at ambient and high pressure up to 7 GPa by Raman scattering and electronic structure calculations. The behavior of optical phonons is studied experimentally with a diamond anvil cell and computationally through density functional theory calculations.

Influence of thermostatting on nonequilibrium molecular dynamics simulations of heat conduction in solids.

Nonequilibrium molecular dynamics (NEMD) has been extensively used to study thermal transport at various length scales in many materials. In this method, two local thermostats at different temperatures are used to generate a nonequilibrium steady state with a constant heat flux. Conventionally, the thermal conductivity of a finite system is calculated as the ratio between the heat flux and the temperature gradient extracted from the linear part of the temperature profile away from the local thermostats.

Publisher Correction: An electrochemical thermal transistor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Quasi-Ballistic Thermal Transport Across MoS Thin Films.

Layered two-dimensional (2D) materials have highly anisotropic thermal properties between the in-plane and cross-plane directions. Conventionally, it is thought that cross-plane thermal conductivities (κ ) are low, and therefore c-axis phonon mean free paths (MFPs) are small. Here, we measure κ across MoS films of varying thickness (20-240 nm) and uncover evidence of very long c-axis phonon MFPs at room temperature in these layered semiconductors.

An electrochemical thermal transistor.

The ability to actively regulate heat flow at the nanoscale could be a game changer for applications in thermal management and energy harvesting. Such a breakthrough could also enable the control of heat flow using thermal circuits, in a manner analogous to electronic circuits. Here we demonstrate switchable thermal transistors with an order of magnitude thermal on/off ratio, based on reversible electrochemical lithium intercalation in MoS thin films.

Efficient thermal diode with ballistic spacer.

Thermal rectification is of importance not only for fundamental physics, but also for potential applications in thermal manipulations and thermal management. However, thermal rectification effect usually decays rapidly with system size. Here, we show that a mass-graded system, with two diffusive leads separated by a ballistic spacer, can exhibit large thermal rectification effect, with the rectification factor independent of system size.

Anisotropy Enhancement of Thermal Energy Transport in Supported Black Phosphorene.

Thermal anisotropy along the basal plane of materials possesses both theoretical importance and application value in thermal transport and thermoelectricity. Though common two-dimensional materials may exhibit in-plane thermal anisotropy when suspended, thermal anisotropy would often disappear when supported on a substrate. In this Letter, we find a strong anisotropy enhancement of thermal energy transport in supported black phosphorene.

Thermoelectricity of interacting particles: a numerical approach.

A method for computing the thermopower in interacting systems is proposed. This approach, which relies on Monte Carlo simulations, is illustrated first for a diatomic chain of hard-point elastically colliding particles and then in the case of a one-dimensional gas with (screened) Coulomb interparticle interaction. Numerical simulations up to N>10^{4} particles confirm the general theoretical arguments for momentum-conserving systems and show that the thermoelectric figure of merit increases linearly with the system size.

Finite-size effects on current correlation functions.

We study why the calculation of current correlation functions (CCFs) still suffers from finite-size effects even when the periodic boundary condition is taken. Two important one-dimensional, momentum-conserving systems are investigated as examples. Intriguingly, it is found that the state of a system recurs in the sense of microcanonical ensemble average, and such recurrence may result in oscillations in CCFs.

Nonintegrability and the Fourier heat conduction law.

We study in momentum-conserving systems, how nonintegrable dynamics may affect thermal transport properties. As illustrating examples, two one-dimensional (1D) diatomic chains, representing 1D fluids and lattices, respectively, are numerically investigated. In both models, the two species of atoms are assigned two different masses and are arranged alternatively.