284 research outputs found
On the classification and dispersability of circulant graphs with two jump lengths
In this paper, we give the classification of circulant graphs
with and completely solve the dispersability of
circulant graphs
Enhancing thermoelectric figure-of-merit by low-dimensional electrical transport in phonon-glass crystals
Low-dimensional electronic and glassy phononic transport are two important
ingredients of highly-efficient thermoelectric material, from which two
branches of the thermoelectric research emerge. One focuses on controlling
electronic transport in the low dimension, while the other on multiscale phonon
engineering in the bulk. Recent work has benefited much from combining these
two approaches, e.g., phonon engineering in low-dimensional materials. Here, we
propose to employ the low-dimensional electronic structure in bulk phonon-glass
crystal as an alternative way to increase the thermoelectric efficiency.
Through first-principles electronic structure calculation and classical
molecular dynamics simulation, we show that the - stacking
Bis-Dithienothiophene molecular crystal is a natural candidate for such an
approach. This is determined by the nature of its chemical bonding. Without any
optimization of the material parameter, we obtain a maximum room-temperature
figure of merit, , of at optimal doping, thus validating our idea.Comment: Nano Lett.201
Thermal conductivity of MgO in giant planetary interior conditions predicted by deep potential
Thermal conductivity of MgO plays a fundamental role in
understanding the thermal evolution and mantle convection in the interior of
terrestrial planets. However, previous theoretical calculations deviate from
each other and the of high-pressure B2 phase remains undetermined.
Here, by combining molecular dynamics and deep potential trained with
first-principles data, we systematically investigate the of MgO from
ambient state to the core-mantle boundary (CMB) of super-Earth with
. We point out the significance of 4-phonon scatterings and modify
the conventional thermal conductivity model of MgO by considering the
density-dependent proportion of 3-phonon and 4-phonon scatterings. The
profiles of MgO in Earth and super-Earth are further estimated. For
super-Earth, we predict a significant reduction of at the B1-B2 phase
transition area near the CMB. This work provides new insights into thermal
transport under extreme conditions and an improved thermal model for
terrestrial planets.Comment: 4 figure
Anomalous thermal transport across the superionic transition in ice
Superionic ices with highly mobile protons within the stable oxygen
sub-lattice occupy an important proportion of the phase diagram of ice and
widely exist in the interior of icy giants and throughout the universe.
Understanding the thermal transport in superionic ice is vital for the thermal
evolution of icy planets. However, it is highly challenging due to the extreme
thermodynamic conditions and dynamical nature of protons, beyond the capability
of the traditional lattice dynamics and empirical potential molecular dynamics
approaches. In this work, by utilizing the deep potential molecular dynamics
approach, we investigate the thermal conductivity of ice-VII and superionic
ice-VII" along the isobar of . A non-monotonic trend of
thermal conductivity with elevated temperature is observed. Through heat flux
decomposition and trajectory-based spectra analysis, we show that the
thermally-activated proton diffusion in ice-VII and superionic ice-VII"
contribute significantly to heat convection, while the broadening in
vibrational energy peaks and significant softening of transverse acoustic
branches lead to a reduction in heat conduction. The competition between proton
diffusion and phonon scattering results in anomalous thermal transport across
the superionic transition in ice. This work unravels the important role of
proton diffusion in the thermal transport of high-pressure ice. Our approach
provides new insights into modeling the thermal transport and atomistic
dynamics in superionic materials.Comment: 5 figure
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