67 research outputs found
Diverse Thermal Transport Properties of Two-Dimensional Materials: A Comparative Review
The discovery of graphene led to an upsurge in exploring two-dimensional (2D) materials, such as silicene, germanene, phosphorene, hexagonal boron nitride (h-BN), and transition metal dichalcogenides (TMDCs), which have attracted tremendous attention due to their unique dimension-dependent properties in the applications of nanoelectronics, optoelectronics, and thermoelectrics. The phonon transport properties governing the heat energy transfer have become a crucial issue for continuing progress in the electronic industry. This chapter reviews the state-of-the-art theoretical and experimental investigations of phonon transport properties of broad 2D nanostructures in various forms, with graphene, silicene and phosphorene as representatives, all of which consist of single element. Special attention is given to the effect of different physical factors, such as sample size, strain, and layer thickness. The effect of substrate and the phonon transport properties in heterostructures are also discussed. We find that the phonon transport properties of 2D materials largely depend on their atomic structure and interatomic bonding nature, showing a diverse intrinsic phonon behavior and disparate response to external environment
Anisotropic intrinsic lattice thermal conductivity of phosphorene from first principles
Phosphorene, the single layer counterpart of black phosphorus, is a novel
two-dimensional semiconductor with high carrier mobility and a large
fundamental direct band gap, which has attracted tremendous interest recently.
Its potential applications in nano-electronics and thermoelectrics call for a
fundamental study of the phonon transport. Here, we calculate the intrinsic
lattice thermal conductivity of phosphorene by solving the phonon Boltzmann
transport equation (BTE) based on first-principles calculations. The thermal
conductivity of phosphorene at is
(zigzag) and
(armchair), showing an obvious anisotropy along different directions. The
calculated thermal conductivity fits perfectly to the inverse relation with
temperature when the temperature is higher than Debye temperature (). In comparison to graphene, the minor contribution around
of the ZA mode is responsible for the low thermal conductivity of
phosphorene. In addition, the representative mean free path (MFP), a critical
size for phonon transport, is also obtained.Comment: 5 pages and 6 figures, Supplemental Material available as
http://www.rsc.org/suppdata/cp/c4/c4cp04858j/c4cp04858j1.pd
Methodology for determining the electronic thermal conductivity of metals via direct non-equilibrium ab initio molecular dynamics
Many physical properties of metals can be understood in terms of the free
electron model, as proven by the Wiedemann-Franz law. According to this model,
electronic thermal conductivity () can be inferred from the
Boltzmann transport equation (BTE). However, the BTE does not perform well for
some complex metals, such as Cu. Moreover, the BTE cannot clearly describe the
origin of the thermal energy carried by electrons or how this energy is
transported in metals. The charge distribution of conduction electrons in
metals is known to reflect the electrostatic potential (EP) of the ion cores.
Based on this premise, we develop a new methodology for evaluating
by combining the free electron model and non-equilibrium ab
initio molecular dynamics (NEAIMD) simulations. We demonstrate that the kinetic
energy of thermally excited electrons originates from the energy of the spatial
electrostatic potential oscillation (EPO), which is induced by the thermal
motion of ion cores. This method directly predicts the of pure
metals with a high degree of accuracy.Comment: 7 pages, 3 figures, with Supplementary Information of 19 pages, 7
figures and 7 table
Diverse anisotropy of phonon transport in two-dimensional IV-VI compounds: A comparative study
New classes two-dimensional (2D) materials beyond graphene, including layered
and non-layered, and their heterostructures, are currently attracting
increasing interest due to their promising applications in nanoelectronics,
optoelectronics and clean energy, where thermal transport property is one of
the fundamental physical parameters. In this paper, we systematically
investigated the phonon transport properties of 2D orthorhombic group IV-VI
compounds of , , and by solving the Boltzmann transport
equation (BTE) based on first-principles calculations. Despite the similar
puckered (hinge-like) structure along the armchair direction as phosphorene,
the four monolayer compounds possess diverse anisotropic properties in many
aspects, such as phonon group velocity, Young's modulus and lattice thermal
conductivity (), etc. Especially, the along the zigzag and
armchair directions of monolayer shows the strongest anisotropy while
monolayer and shows an almost isotropy in phonon transport. The
origin of the diverse anisotropy is fully studied and the underlying mechanism
is discussed in detail. With limited size, the could be effectively
lowered, and the anisotropy could be effectively modulated by nanostructuring,
which would extend the applications in nanoscale thermoelectrics and thermal
management. Our study offers fundamental understanding of the anisotropic
phonon transport properties of 2D materials, and would be of significance for
further study, modulation and aplications in emerging technologies.Comment: 14 pages, 8 figures, 2 table
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High hydrostatic pressure harnesses the biosynthesis of secondary metabolites via the regulation of polyketide synthesis genes of hadal sediment-derived fungi
Deep-sea fungi have evolved extreme environmental adaptation and possess huge biosynthetic potential of bioactive compounds. However, not much is known about the biosynthesis and regulation of secondary metabolites of deep-sea fungi under extreme environments. Here, we presented the isolation of 15 individual fungal strains from the sediments of the Mariana Trench, which were identified by internal transcribed spacer (ITS) sequence analysis as belonging to 8 different fungal species. High hydrostatic pressure (HHP) assays were performed to identify the piezo-tolerance of the hadal fungi. Among these fungi, Aspergillus sydowii SYX6 was selected as the representative due to the excellent tolerance of HHP and biosynthetic potential of antimicrobial compounds. Vegetative growth and sporulation of A. sydowii SYX6 were affected by HHP. Natural product analysis with different pressure conditions was also performed. Based on bioactivity-guided fractionation, diorcinol was purified and characterized as the bioactive compound, showing significant antimicrobial and antitumor activity. The core functional gene associated with the biosynthetic gene cluster (BGC) of diorcinol was identified in A. sydowii SYX6, named as AspksD. The expression of AspksD was apparently regulated by the HHP treatment, correlated with the regulation of diorcinol production. Based on the effect of the HHP tested here, high pressure affected the fungal development and metabolite production, as well as the expression level of biosynthetic genes which revealed the adaptive relationship between the metabolic pathway and the high-pressure environment at the molecular level
Thermal transport properties of monolayer phosphorene: a mini-review of theoretical studies
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