Lattice thermal conductivity(κlat)of MgSiO_(3) perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth.Here,we develop a deep potential of density functional theory quality unde...Lattice thermal conductivity(κlat)of MgSiO_(3) perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth.Here,we develop a deep potential of density functional theory quality under entire thermodynamic conditions in the lower mantle,and calculate theκlatby the Green-Kubo relation.Deep potential molecular dynamics captures full-order anharmonicity and considers ill-defined phonons in low-κlatmaterials ignored in the phonon gas model.Theκlatshows negative temperature dependence and positive linear pressure dependence.Interestingly,theκlatundergos an increase at the phase boundary from perovskite to post-perovskite.We demonstrate that,along the geotherm,theκlatincreases by 18.2% at the phase boundary.Our results would be helpful for evaluating Earth’s thermal dynamics and improving the Earth model.展开更多
Superionic ices with highly mobile protons within stable oxygen sub-lattices occupy an important proportion of the phase diagram of ice and widely exist in the interior of icy giants and throughout the Universe.Unders...Superionic ices with highly mobile protons within stable oxygen sub-lattices 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.By utilizing the deep potential molecular dynamics approach,we investigate the thermal conductivity of ice-Ⅶ and superionic ice-Ⅶ’’ along the isobar of P = 30 GPa.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.展开更多
We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hind...We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hindrance in phonon transport.Here we propose that the vdW confinement can enhance phonon transport.Through molecular dynamics simulations,it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon.The quantitative analyses of morphology,local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism.It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes,leading to less phonon scattering and facilitating thermal transport.Our study offers a new strategy to modulate the phonon transport.展开更多
Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance are of great importance for thermal management and modulation.Herein,the interfacial thermal resistance between ...Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance are of great importance for thermal management and modulation.Herein,the interfacial thermal resistance between overlapped graphene nanoribbons is largely reduced by adding bonded carbon chains as shown by molecular dynamics simulations.And the analytical model(phonon weak couplings model,PWCM)is utilized to analyze and explain the two-dimensional thermal transport mechanism at the cross-interface.An order of magnitude reduction of the interfacial thermal resistance is found as the graphene nanoribbons are bonded by just one carbon chain.Interestingly,the decreasing rate of the interfacial thermal resistance slows down gradually with the increasing number of carbon chains,which can be explained by the proposed theoretical relationship based on analytical model.Moreover,by the comparison of PWCM and the traditional simplified model,the accuracy of PWCM is demonstrated in the overlapped graphene nanoribbons.This work provides a new way to improve the interfacial thermal transport and reveal the essential mechanism for low-dimensional materials applied in thermal management.展开更多
Exploring the novel structural phase of van der Waals(vdW) magnets would promote the development of spintronics.Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrT...Exploring the novel structural phase of van der Waals(vdW) magnets would promote the development of spintronics.Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrTe2, which is one of the popular vdW magnets normally exhibiting a trigonal structure. The new monoclinic phase emerges from a switchable magnetic state between ferromagnetism and antiferromagnetism through changing hole doping concentration, which suggests a practical approach to obtain such a structure. The results of phonon dispersion and energy analysis convince us that the monoclinic structure is a metastable phase even without hole doping. When the hole doping concentration increases,the stability analysis indicates the preference for a novel monoclinic phase rather than a conventional trigonal phase, and meanwhile, the magnetic properties are accordingly tuned. This work provides new insights into the phase engineering of the chalcogenide family and the electrical control of magnetism of vdW layered magnets.展开更多
Optical fine-tunable layer-hybridized Moiréexcitons are highly in demand for emerging many-body states in two-dimensional semiconductors.We report naturally confined layer-hybridized bright Moiréexcitons wit...Optical fine-tunable layer-hybridized Moiréexcitons are highly in demand for emerging many-body states in two-dimensional semiconductors.We report naturally confined layer-hybridized bright Moiréexcitons with long lifetimes in twisted hexagonal GaTe bilayers,using ab initio many-body perturbation theory and the Bethe–Salpeter equation.Due to the hybridization of electrons and holes between layers,which enhances the brightness of excitons,the twisted bilayer system becomes attractive for optical applications.We find that in both R and H-type stacking Moirésuperlattices,more than 200 meV lateral quantum confinements occur on exciton energies,which results in two scenarios:(1)The ground state bright excitons XA are found to be trapped at two high-symmetry points,with opposite electric dipoles in the R-stacking Moirésupercell,forming a honeycomb superlattice of nearest-neighbor dipolar attraction.(2)For H-stacking case,the XA is found to be trapped at only one high-symmetry point exhibiting a triangular superlattice.Our results suggest that twisted h-GaTe bilayer is one of the promising systems for optical fine-tunable excitonic devices and provide an ideal platform for realizing strong correlated Bose–Hubbard physics.展开更多
Leidenfrost effect is a common and important phenomenon which has many applications,however there is a limited body of knowledge about the Leidenfrost effect at the nanoscale regime.We investigate the impact of substr...Leidenfrost effect is a common and important phenomenon which has many applications,however there is a limited body of knowledge about the Leidenfrost effect at the nanoscale regime.We investigate the impact of substrate wettability on Leidenfrost point temperature(LPT) of nanoscale water film via molecular dynamics simulations,and reveal a new mechanism different from that at the macroscale.In the molecular dynamics simulations,a method of monitoring density change at different heating rates is proposed to obtain accurate LPT under different surface wettability.The results show that LPT decreases firstly and then increases with the surface wettability at the nanoscale,which is different from the monotonous increasing trend at the macroscale.The mechanism is elucidated by analyzing the competitive effect of adhesion force and interfacial thermal resistance,as well as different contributions of gravity on LPT at the nanoscale and macroscale.The investigations can deepen the understanding of Leidenfrost effect at the nanoscale regime and also facilitate to guide the applications of heat transfer and flow transport.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U1830206)the National Key R&D Program of China(Grant No.2017YFA0403200)+1 种基金the National Natural Science Foundation of China(Grant Nos.11874424,11904401,11974423,and 12104507)the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC4026)。
文摘Lattice thermal conductivity(κlat)of MgSiO_(3) perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth.Here,we develop a deep potential of density functional theory quality under entire thermodynamic conditions in the lower mantle,and calculate theκlatby the Green-Kubo relation.Deep potential molecular dynamics captures full-order anharmonicity and considers ill-defined phonons in low-κlatmaterials ignored in the phonon gas model.Theκlatshows negative temperature dependence and positive linear pressure dependence.Interestingly,theκlatundergos an increase at the phase boundary from perovskite to post-perovskite.We demonstrate that,along the geotherm,theκlatincreases by 18.2% at the phase boundary.Our results would be helpful for evaluating Earth’s thermal dynamics and improving the Earth model.
基金supported by the National Natural Science Foundation of China(Grant Nos.11874424,12122103,and 12304307)the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC4026)。
文摘Superionic ices with highly mobile protons within stable oxygen sub-lattices 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.By utilizing the deep potential molecular dynamics approach,we investigate the thermal conductivity of ice-Ⅶ and superionic ice-Ⅶ’’ along the isobar of P = 30 GPa.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.
基金Supported by the National Natural Science Foundation of China(Grant Nos.51606072 and 51576077).
文摘We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hindrance in phonon transport.Here we propose that the vdW confinement can enhance phonon transport.Through molecular dynamics simulations,it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon.The quantitative analyses of morphology,local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism.It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes,leading to less phonon scattering and facilitating thermal transport.Our study offers a new strategy to modulate the phonon transport.
基金Project supported by the National Natural Science Foundation of China(Grant No.51606072)the Fundamental Research Funds for the Central Universities,HUST,China(Grant No.2019kfyRCPY045)。
文摘Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance are of great importance for thermal management and modulation.Herein,the interfacial thermal resistance between overlapped graphene nanoribbons is largely reduced by adding bonded carbon chains as shown by molecular dynamics simulations.And the analytical model(phonon weak couplings model,PWCM)is utilized to analyze and explain the two-dimensional thermal transport mechanism at the cross-interface.An order of magnitude reduction of the interfacial thermal resistance is found as the graphene nanoribbons are bonded by just one carbon chain.Interestingly,the decreasing rate of the interfacial thermal resistance slows down gradually with the increasing number of carbon chains,which can be explained by the proposed theoretical relationship based on analytical model.Moreover,by the comparison of PWCM and the traditional simplified model,the accuracy of PWCM is demonstrated in the overlapped graphene nanoribbons.This work provides a new way to improve the interfacial thermal transport and reveal the essential mechanism for low-dimensional materials applied in thermal management.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0403200)the National Natural Science Foundation of China (Grant No. 11774429)+1 种基金the NSAF (Grant No. U1830206)the Science and Technology Innovation Program of Hunan Province, China (Grant No. 2021RC4026)。
文摘Exploring the novel structural phase of van der Waals(vdW) magnets would promote the development of spintronics.Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrTe2, which is one of the popular vdW magnets normally exhibiting a trigonal structure. The new monoclinic phase emerges from a switchable magnetic state between ferromagnetism and antiferromagnetism through changing hole doping concentration, which suggests a practical approach to obtain such a structure. The results of phonon dispersion and energy analysis convince us that the monoclinic structure is a metastable phase even without hole doping. When the hole doping concentration increases,the stability analysis indicates the preference for a novel monoclinic phase rather than a conventional trigonal phase, and meanwhile, the magnetic properties are accordingly tuned. This work provides new insights into the phase engineering of the chalcogenide family and the electrical control of magnetism of vdW layered magnets.
基金the National Key R&D Program of China(Grant No.2017YFA0403200)the National Natural Science Foundation of China(Grant No.U1830206)the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC4026)。
文摘Optical fine-tunable layer-hybridized Moiréexcitons are highly in demand for emerging many-body states in two-dimensional semiconductors.We report naturally confined layer-hybridized bright Moiréexcitons with long lifetimes in twisted hexagonal GaTe bilayers,using ab initio many-body perturbation theory and the Bethe–Salpeter equation.Due to the hybridization of electrons and holes between layers,which enhances the brightness of excitons,the twisted bilayer system becomes attractive for optical applications.We find that in both R and H-type stacking Moirésuperlattices,more than 200 meV lateral quantum confinements occur on exciton energies,which results in two scenarios:(1)The ground state bright excitons XA are found to be trapped at two high-symmetry points,with opposite electric dipoles in the R-stacking Moirésupercell,forming a honeycomb superlattice of nearest-neighbor dipolar attraction.(2)For H-stacking case,the XA is found to be trapped at only one high-symmetry point exhibiting a triangular superlattice.Our results suggest that twisted h-GaTe bilayer is one of the promising systems for optical fine-tunable excitonic devices and provide an ideal platform for realizing strong correlated Bose–Hubbard physics.
基金Supported by the National Key Research and Development Program of China(Grant No.2018YFE0127800)。
文摘Leidenfrost effect is a common and important phenomenon which has many applications,however there is a limited body of knowledge about the Leidenfrost effect at the nanoscale regime.We investigate the impact of substrate wettability on Leidenfrost point temperature(LPT) of nanoscale water film via molecular dynamics simulations,and reveal a new mechanism different from that at the macroscale.In the molecular dynamics simulations,a method of monitoring density change at different heating rates is proposed to obtain accurate LPT under different surface wettability.The results show that LPT decreases firstly and then increases with the surface wettability at the nanoscale,which is different from the monotonous increasing trend at the macroscale.The mechanism is elucidated by analyzing the competitive effect of adhesion force and interfacial thermal resistance,as well as different contributions of gravity on LPT at the nanoscale and macroscale.The investigations can deepen the understanding of Leidenfrost effect at the nanoscale regime and also facilitate to guide the applications of heat transfer and flow transport.
