Thermal expansion is crucial for various industrial processes and is increasingly the focus of research endeavors aimed at improving material performance.However,it is the continuous advancements in first-principles c...Thermal expansion is crucial for various industrial processes and is increasingly the focus of research endeavors aimed at improving material performance.However,it is the continuous advancements in first-principles calculations that have enabled researchers to understand the microscopic origins of thermal expansion.In this study,we propose a coefficient of thermal expansion(CTE)calculation scheme based on self-consistent phonon theory,incorporating the fourth-order anharmonicity.We selected four structures(Si,CaZrF_(6),SrTiO_(3),NaBr)to investigate high-order anharmonicity’s impact on their CTEs,based on bonding types.The results indicate that our method goes beyond the second-order quasi-harmonic approximation and the third-order perturbation theory,aligning closely with experimental data.Furthermore,we observed that an increase in the ionicity of the structures leads to a more pronounced influence of high-order anharmonicity on CTE,with this effect primarily manifesting in variations of the Grüneisen parameter.Our research provides a theoretical foundation for accurately predicting and regulating the thermal expansion behavior of materials.展开更多
As a typical (IV–VI)_(x)(V_(2)VI_(3))_(y) compound, the tetradymite-like layered SnSb_(2)Te_(4) -based compounds have attracted increasing attention in the thermoelectric community owing to the intrinsically low latt...As a typical (IV–VI)_(x)(V_(2)VI_(3))_(y) compound, the tetradymite-like layered SnSb_(2)Te_(4) -based compounds have attracted increasing attention in the thermoelectric community owing to the intrinsically low lattice thermal conductivity. Nevertheless, the effect of cations disorder on the inherent physical characteristics remains puzzling, and its inferior Seebeck coefficient is the bottleneck to achieving high thermoelectric performance. In this work, the thermoelectric properties of polycrystalline In_(x)Sn_(1−x)Sb_(2)(Te_(1−y)Se_(y))_(4) (0≤x≤0.1,0≤y≤0.15) samples are comprehensively investigated. In conjunction with the calculated band structure and experimental results, the Seebeck coefficient and power factor are markedly improved after the introduction of indium and selenium, which originates from the combined effects of the emergent resonant states and converged valence bands along with optimal carrier concentration. Additionally, compared with the ordered lattice structure, the disordered cations occupancy in SnSb_(2)Te_(4) further strengthens lattice anharmonicity and reduces phonon group velocity verified by first-principles calculations, securing intrinsically low lattice thermal conductivity. Finally, a record zT value of ∼0.6 at 670 K and an average zT of ∼0.4 between 320 and 720 K are obtained in the In0.1 Sn0.9 Sb2 Te3.4 Se0.6 sample, being one of the highest zT values among SnSb2 Te4 -based materials. This work not only demonstrates that SnSb2 Te4 -based compounds are promising thermoelectric candidates, but also provides guidance for the promotion of thermoelectric performance in a broad temperature range.展开更多
The thermoelectric properties of layered Mo_(2)AB_(2)(A=S,Se,Te;B=Cl,Br,I)materials are systematically investigated by first-principles approach.Soft transverse acoustic modes and direct Mo d–Mo d couplings give rise...The thermoelectric properties of layered Mo_(2)AB_(2)(A=S,Se,Te;B=Cl,Br,I)materials are systematically investigated by first-principles approach.Soft transverse acoustic modes and direct Mo d–Mo d couplings give rise to strong anharmonicities and low lattice thermal conductivities.The double anions with distinctly different electronegativities of Mo_(2)AB_(2)monolayers can reduce the correlation between electron transport and phonon scattering,and further benefit much to their good thermoelectric properties.Thermoelectric properties of these Mo_(2)AB_(2)monolayers exhibit obvious anisotropies due to the direction-dependent chemical bondings and transport properties.Furthermore,their thermoelectric properties strongly depend on carrier type(n-type or p-type),carrier concentration and temperature.It is found that n-type Mo_(2)AB_(2)monolayers can be excellent thermoelectric materials with high electric conductivity,σ,and figures of merit,ZT.Choosing the types of A and B anions of Mo_(2)AB_(2)is an effective strategy to optimize their thermoelectric performance.These results provide rigorous understanding on thermoelectric properties of double-anions compounds and important guidance for achieving high thermoelectric performance in multi-anion compounds.展开更多
Nonisovalent(GaN)_(1-x)(ZnO)_(x)alloys are more technologically promising than their binary counterparts because of the abruptly reduced band gap.Unfortunately,the lack of two-dimensional(2D)configurations as well as ...Nonisovalent(GaN)_(1-x)(ZnO)_(x)alloys are more technologically promising than their binary counterparts because of the abruptly reduced band gap.Unfortunately,the lack of two-dimensional(2D)configurations as well as complete stoichiometries hinders to further explore the thermal transport,thermoelectrics,and adsorption/permeation.We identify that multilayer(GaN)_(1-x)(ZnO)_(x)stabilize as wurtzite-like Pm-(GaN)_(3)(ZnO)_(1),Pmc2_(1)-(Ga N)_(1)(ZnO)_(1),P3m1-(GaN)_(1)(ZnO)_(2),and haeckelite C2/m-(GaN)_(1)(ZnO)_(3)via structural searches.P3m1-(GaN)_(1)(ZnO)_(2)shares the excellent thermoelectrics with the figure of merit ZT as high as 3.08 at 900 K for the p-type doping due to the ultralow lattice thermal conductivity,which mainly arises from the strong anharmonicity by the interlayer asymmetrical charge distributions.The p–d coupling is prohibited from the group theory in C2/m-(Ga N)_(1)(ZnO)_(3),which thereby results in the anomalous band structure versus Zn O composition.To unveil the adsorption/permeation of H^(+),Na^(+),and OH^(-)ions in AA-stacking configurations,the potential wells and barriers are explored from the Coulomb interaction and the ionic size.Our work is helpful in experimental fabrication of novel optoelectronic and thermoelectric devices by 2D(GaN)_(1-x)(ZnO)_(x)alloys.展开更多
Quantum nuclear effects and anharmonicity impact a wide range of functional materials and their properties.One of the most powerful techniques to model these effects is the Stochastic Self-Consistent Harmonic Approxim...Quantum nuclear effects and anharmonicity impact a wide range of functional materials and their properties.One of the most powerful techniques to model these effects is the Stochastic Self-Consistent Harmonic Approximation(SSCHA).Unfortunately,the SSCHA is extremely computationally expensive,prohibiting its routine use.We propose a protocol that pairs machine learning interatomic potentials,which can be tailored for the system at hand via active learning,with the SSCHA.Our method leverages an upscaling procedure that allows for the treatment of supercells of up to thousands of atoms with practically minimal computational effort.The protocol is applied to PdCuH_(x)(x=0−2)compounds,chosen because previous experimental studies have reported superconducting critical temperatures,Tcs,as high as 17 K at ambient pressures in an unknown hydrogenated PdCu phase.We identify a P4/mmm PdCuH_(2)structure,which is shown to be dynamically stable only upon the inclusion of quantum fluctuations,as being a key contributor to the measured superconductivity.For this system,our methodology is able to reduce the computational expense for the SSCHA calculations by~96%.The proposed protocol opens the door towards the routine inclusion of quantum nuclear motion and anharmonicity in materials discovery.展开更多
The Raman activeGmode in graphene exhibits a strong coupling to electrons,yet the comprehensive treatment of this interaction in the calculation of its temperature-dependent Raman spectrumremains incomplete.In this st...The Raman activeGmode in graphene exhibits a strong coupling to electrons,yet the comprehensive treatment of this interaction in the calculation of its temperature-dependent Raman spectrumremains incomplete.In this study,we calculate the temperature dependence of the G-mode frequency and linewidth,and successfully explain the experimental trend by accounting for the contributions arising from the first-order electron-phonon coupling,electron-mediated phonon-phonon coupling,and standard lattice anharmonicity.The generality of our approach enables its broad applicability to study phonon dynamics in materials where both electron-phonon coupling and anharmonicity are important.展开更多
In this work,we develop an extended dissipaton theory that generalizes the environmental couplings beyond the conventional linear and quadratic forms,enabling the treatment of ar-bitrary order of bath couplings.Ap-ply...In this work,we develop an extended dissipaton theory that generalizes the environmental couplings beyond the conventional linear and quadratic forms,enabling the treatment of ar-bitrary order of bath couplings.Ap-plying this theoretical framework to the condensed-phase non-Condon spectroscopy,we demonstrate the in-terplay of anharmonicity,non-Con-don and solvent effects on optical spectra,where the higher-order cou-plings arise from the anharmonicity of nuclear potential surface of the excited state.Precise simulations are carried out with high efficiency on linear absorption spectra involving the above mentioned correlated effects.We exhibit how an anharmonic potential modulates the vibronic feature,offering insights into the role of nonlinear environmental couplings in spectroscopic signatures and exemplifying the success of the extended dissipaton formalism as an exact and efficient method for higher-or-der bath couplings.展开更多
Pressure serves as a powerful approach to regulating the thermal conductivity of materials.By applying pressure,one can alter the lattice symmetry,atomic spacing,and phonon scattering mechanisms,thereby exerting a pro...Pressure serves as a powerful approach to regulating the thermal conductivity of materials.By applying pressure,one can alter the lattice symmetry,atomic spacing,and phonon scattering mechanisms,thereby exerting a profound influence on thermal transport properties.SnS,sharing the same crystal structure as SnSe,has often been overlooked due to its higher lattice thermal conductivity.While extensive efforts have been dedicated to enhancing the power factor of SnS through doping,its thermal transport properties remain underexplored,limiting its potential as a thermoelectric material.In this study,we investigated the impact of pressure modulation on the thermoelectric performance of SnS.Remarkably,the application of negative pressure significantly enhanced its thermal transport characteristics,leading to a reduction in the lattice thermal conductivity(κL)along the axis to 0.23 W/(m·K)at 800 K,on par with that of SnSe.Despite the negligible improvement in carrier mobility under negative pressure,the electronic transport properties were preserved within an acceptable range.Most notably,a maximum ZT value of 2.7 was achieved along the axis at 800 K,marking a substantial advancement in the thermoelectric performance of n-type SnS.展开更多
Metal-stuffed B–C compounds with sodalite clathrate structure have captured increasing attention due to their predicted exceptional superconductivity above liquid nitrogen temperature at ambient pressure.However,by n...Metal-stuffed B–C compounds with sodalite clathrate structure have captured increasing attention due to their predicted exceptional superconductivity above liquid nitrogen temperature at ambient pressure.However,by neglecting the quantum lattice anharmonicity,the existing studiesmay result in an incomplete understanding of such a lightweight system.Here,using state-of-the-art ab initio methods incorporating quantum effects and machine learning potentials,we revisit the properties of a series of XYB_(6)C_(6)clathrates where X and Y are metals.Our findings show that ionic quantum and anharmonic effects can harden the E_(g)and E_(u)vibrational modes,enabling the dynamical stability of 15 materials previously considered unstable in the harmonic approximation,including materials with previously unreported (XY)^(1+)state,which is demonstrated here to be crucial to reach high critical temperatures.Further calculations based on the anisotropic Migdal-Eliashberg equation demonstrate that the T_(c)values for KRbB_(6)C_(6)and RbB_(3)C_(3)among these stabilized compounds are 102 and 115 Kat 0 and 15 GPa,respectively,both being higher than T_(c)of 92 K of KPbB_(6)C_(6)at the anharmonic level.These record-high T_(c)values,surpassing liquid nitrogen temperatures,emphasize the importance of anharmonic effects in stabilizing B-C clathrates with large electron-phonon coupling strength and advancing the search for high-T_(c)superconductivity at(near)ambient pressure.展开更多
Thermal properties are essentially decided by atomic geometry and thus stress is the most direct way for manipulating. In this paper, we investigate stress modulation of thermal conductivity of graphene by molecular d...Thermal properties are essentially decided by atomic geometry and thus stress is the most direct way for manipulating. In this paper, we investigate stress modulation of thermal conductivity of graphene by molecular dynamics simulations and discuss the underlying microscopic mechanism. It is found that thermal conductivity of ftexural-free graphene increases with compression and decreases with strain, while thermal conductivity of flexural-included graphene decreases with both compression and strain. Such difference in thermal behavior originates from the changes in the anharmonicity of the interatomic potential, where the wrinkle scattering is responsible for the thermal conductivity diminishment in flexural-included graphene under strain. By comparing the results obtained from the Tersoff and AIREBO potentials, it is revealed that the degree of the symmetry of interatomic potential determines the thermal conductivity variation of graphene. Our results indicate that the symmetry of interatomic potential should be taken into careful consideration in constructing the lattice model of graphene.展开更多
Anharmonic lattice vibrations play pivotal roles in the thermal dynamics in condense matters and affect how the atoms interact and conduct heat.An in-depth understanding of the microscopic mechanism of phonon anharmon...Anharmonic lattice vibrations play pivotal roles in the thermal dynamics in condense matters and affect how the atoms interact and conduct heat.An in-depth understanding of the microscopic mechanism of phonon anharmonicity in condensed systems is critical for developing better functional and energy materials.In recent years,various novel behaviors in condense matters driven by phonon anharmonic effects were discovered,such as soft mode phase transition,negative thermal expansion(NTE),multiferroicity,ultralow thermal conductivity(κ),high thermal resistance,and high-temperature superconductivity.These properties have endowed anharmonicity with many promising applications and provided remarkable opportunities for developing“Anharmonicity Engineering”-regulating heat transport towards excellent performance in materials.In this work,we review the recent development of studies on phonon anharmonic effect and summarize its origin,mechanism,research methods,and applications.Besides,the remaining challenges,future trends,and prospects of phonon anharmonicity are also discussed.展开更多
Two-dimensional(2D) van der Waals(vdW) materials have extraordinary thermal properties due to the effect of quantum confinement, making them promising for thermoelectric energy conversion and thermal management in mic...Two-dimensional(2D) van der Waals(vdW) materials have extraordinary thermal properties due to the effect of quantum confinement, making them promising for thermoelectric energy conversion and thermal management in microelectronic devices.In this review, the mechanism of phonon anharmonicity originating from three-and four-phonon interactions is derived. The phonon anharmonicity of 2D vdW materials, involving the Grüneisen parameter, phonon lifetime, and thermal conductivity, is summarized and derived in detail. The size-dependent thermal conductivity of representative 2D vdW materials is discussed experimentally and theoretically. This review will present fundamental and advanced knowledge on how to evaluate the phonon anharmonicity in 2D vdW materials, which will aid the design of new structures and materials for applications related to energy transfer and conversion.展开更多
Copper(Cu)-based materials(such as cuprates,Cu chalcogenides,and Cu halides)often exhibit unusual properties such as superconductivity,ultralow thermal conductivity,and superionicity.However,the electronic origin of t...Copper(Cu)-based materials(such as cuprates,Cu chalcogenides,and Cu halides)often exhibit unusual properties such as superconductivity,ultralow thermal conductivity,and superionicity.However,the electronic origin of these unusual behaviors remains elusive.In this study,we demonstrate that the high-lying occupied 3d orbital of Cu causes a strong s-d coupling with its unoccupied 4s state when local symmetry is reduced.This leads to strong phonon anharmonicity and is responsible for these intriguing properties.For example,during thermal transport,symmetry-controlled s-d coupling can substantially lower the lattice potential barrier,thereby enhancing the anharmonicity and scattering between phonons and ultimately significantly reducing lattice thermal conductivity.We confirmed this understanding with Raman spectra measurements,which demonstrated a remarkable red shift in the phonon vibrational frequency with an increase in the temperature of Cu-based semiconductors.Our study shows that the cause of phonon anharmonicity is related to the fundamental electronic structures,which can also explain other unusual physical properties of the Cu compounds.展开更多
The hydrogen mean force from experimental neutron Compton profiles is derived using deep inelastic neutron scattering on amorphous and polycrystalline ice. The formalism of mean force is extended to probe its sensitiv...The hydrogen mean force from experimental neutron Compton profiles is derived using deep inelastic neutron scattering on amorphous and polycrystalline ice. The formalism of mean force is extended to probe its sensitivity to anharmonicity in the hydrogen-nucleus effective potential. The shape of the mean force for amorphous and polycrystalline ice is primarily determined by the anisotropy of the underlying quasi-harmonic effective potential. The data from amorphous ice show an additional curvature reflecting the more pronounced anharmonicity of the effective potential with respect to that of ice Ih.展开更多
The thermal switch plays a crucial role in regulating system temperature,protecting devices from overheating,and improving energy efficiency.Achieving a high thermal switching ratio is essential for its practical appl...The thermal switch plays a crucial role in regulating system temperature,protecting devices from overheating,and improving energy efficiency.Achieving a high thermal switching ratio is essential for its practical application.In this study,by utilizing first-principles calculations and semi-classical Boltzmann transport theory,it is found that hole doping with an experimentally achievable concentration of 1.83×10^(14)cm^(-2)can reduce the lattice thermal conductivity of monolayer MoS_(2) from 151.79 W·m^(-1)·K^(-1)to 12.19 W·m^(-1)·K^(-1),achieving a high thermal switching ratio of 12.5.The achieved switching ratio significantly surpasses previously reported values,including those achieved by extreme strain methods.This phenomenon mainly arises from the enhanced lattice anharmonicity,which is primarily contributed by the S atoms.These results indicate that hole doping is an effective method for tuning the lattice thermal conductivity of materials,and demonstrate that monolayer MoS_(2) is a potential candidate material for thermal switches.展开更多
Phonon quasiparticles and their anharmonic interactions govern heat transport in insulators.Accurate characterization of phonon frequencies and linewidths,especially beyond the quasiparticle approximation,is essential...Phonon quasiparticles and their anharmonic interactions govern heat transport in insulators.Accurate characterization of phonon frequencies and linewidths,especially beyond the quasiparticle approximation,is essential for understanding anharmonic effects and lattice thermal conductivity.Here,we investigate the anharmonic lattice dynamics and phonon transport in crystalline copper halides CuBiI_(4) using the self-consistent phonon theory,combined with the Wigner transport formalism and the quasi-harmonic Green–Kubo method.Results show that the three-phonon bubble self-energy substantially renormalizes the phonon dispersion,inducing strong modedependent broadening.Depending on the strength of the anharmonic scattering,phonons exhibit particle-like,wave-like,or overdamped transport characteristics,with broadened states contributing additional coherent thermal transport channels.We establish a consistent description of the overdamped phonon self-energy and advance the microscopic understanding of the strongly anharmonic phonon thermal transport in CuBiI_(4).Overdamped phonon modes significantly hinder the lattice thermal transport by reducing phonon lifetimes.However,the still well-defined phonon dispersions mitigate carrier scattering induced by the local structural disorder.Anisotropic electrical transport properties are obtained by considering polar and non-polar electroacoustic coupling and ionized impurity scattering mechanisms.Upon electron doping,the thermoelectric figure of merit of n-type CuBiI_(4) reaches 2.25 at 800 K.展开更多
The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of thre...The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.展开更多
Lattice thermal conductivity, κL, is a fundamental parameter for evaluating the performance of thermoelectric materials. However, the predicted value of κL based on the Debye dispersion model is often overestimated ...Lattice thermal conductivity, κL, is a fundamental parameter for evaluating the performance of thermoelectric materials. However, the predicted value of κL based on the Debye dispersion model is often overestimated compared with the experimentally determined value.Many researchers have attempted to modify the theoretical model and have sought more reliable results. In this review,the recent progress in the study of phonon dispersion models is summarized and we propose that the lattice thermal conductivity can be most accurately determined by using the modified sinusoidal phonon dispersion model.Moreover, experimental methods that have the potential to reduce a thermoelectric material's κLare reviewed, for example, methods that generate standing waves or anharmonic lattice vibrations. A high concentration of standing waves and anharmonic lattice vibrations can effectively suppress excessive κL. Finally, this review presents the challenges of sinusoidal phonon dispersion when applied to real materials, which are often complicated and therefore time-consuming, especially when dealing with material defects.展开更多
Changes of molecular structure and associated charge distributions, and changes of anharmonic vibrational parameters from DNA base monomers to the Watson-Crick base pairs, have been investigated at the density functio...Changes of molecular structure and associated charge distributions, and changes of anharmonic vibrational parameters from DNA base monomers to the Watson-Crick base pairs, have been investigated at the density functional theory level. Through examination of the NH2, N H, and C=O stretching vibrational modes that are involved in the multiple H-bonds in the base pairs, sensitivity of their diagonal and off-diagonal anharmonicities, as well as anharmonic vibrational couplings, to the structure change are predicted. Our results reveal the intrinsic connection between the anharmonic vibrational potentials, H-bonding, and electrostatic interactions in DNA bases.展开更多
Vibrational and structural dynamics of two transition metal carbonyl complexes, Mn（CO）5Br and Re（CO）5Br were examined in DMSO, using ultrafast infrared pump-probe spectroscopy, steady-state linear infrared spectro...Vibrational and structural dynamics of two transition metal carbonyl complexes, Mn（CO）5Br and Re（CO）5Br were examined in DMSO, using ultrafast infrared pump-probe spectroscopy, steady-state linear infrared spectroscopy and quantum chemistry computations. Two car- bonyl stretching vibrational modes （a low-frequency A1 mode and two high-frequency degenerate E modes） were used as vibrational probes. Central metal effect on the CO bond order and force constant was responsible for a larger E-A1 frequency separation and a generally more red-shifted E and A1 peaks in the Re complex than in the Mn complex. A generally broader spectral width for the A1 mode than the E mode is believed to be partially due to vibrational lifetime effect. Vibrational mode-dependent diagonal anharmonicity was observed in transient infrared spectra, with a generally smaller anharmonicity found for the E mode in both the Mn and Re complexes.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.62125402).
文摘Thermal expansion is crucial for various industrial processes and is increasingly the focus of research endeavors aimed at improving material performance.However,it is the continuous advancements in first-principles calculations that have enabled researchers to understand the microscopic origins of thermal expansion.In this study,we propose a coefficient of thermal expansion(CTE)calculation scheme based on self-consistent phonon theory,incorporating the fourth-order anharmonicity.We selected four structures(Si,CaZrF_(6),SrTiO_(3),NaBr)to investigate high-order anharmonicity’s impact on their CTEs,based on bonding types.The results indicate that our method goes beyond the second-order quasi-harmonic approximation and the third-order perturbation theory,aligning closely with experimental data.Furthermore,we observed that an increase in the ionicity of the structures leads to a more pronounced influence of high-order anharmonicity on CTE,with this effect primarily manifesting in variations of the Grüneisen parameter.Our research provides a theoretical foundation for accurately predicting and regulating the thermal expansion behavior of materials.
基金financially supported in part by the National Natural Science Foundation of China(Grant Nos.52125103,52071041,U21A2054,12204080,11904039,and 12004060)supported in part by the Scientific and Technological Research Program of Chongqing Municipal Education Commission(GrantNo.KJQN202200623)the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX0382)。
文摘As a typical (IV–VI)_(x)(V_(2)VI_(3))_(y) compound, the tetradymite-like layered SnSb_(2)Te_(4) -based compounds have attracted increasing attention in the thermoelectric community owing to the intrinsically low lattice thermal conductivity. Nevertheless, the effect of cations disorder on the inherent physical characteristics remains puzzling, and its inferior Seebeck coefficient is the bottleneck to achieving high thermoelectric performance. In this work, the thermoelectric properties of polycrystalline In_(x)Sn_(1−x)Sb_(2)(Te_(1−y)Se_(y))_(4) (0≤x≤0.1,0≤y≤0.15) samples are comprehensively investigated. In conjunction with the calculated band structure and experimental results, the Seebeck coefficient and power factor are markedly improved after the introduction of indium and selenium, which originates from the combined effects of the emergent resonant states and converged valence bands along with optimal carrier concentration. Additionally, compared with the ordered lattice structure, the disordered cations occupancy in SnSb_(2)Te_(4) further strengthens lattice anharmonicity and reduces phonon group velocity verified by first-principles calculations, securing intrinsically low lattice thermal conductivity. Finally, a record zT value of ∼0.6 at 670 K and an average zT of ∼0.4 between 320 and 720 K are obtained in the In0.1 Sn0.9 Sb2 Te3.4 Se0.6 sample, being one of the highest zT values among SnSb2 Te4 -based materials. This work not only demonstrates that SnSb2 Te4 -based compounds are promising thermoelectric candidates, but also provides guidance for the promotion of thermoelectric performance in a broad temperature range.
基金Project supported by the Science and Technology Program of Guangzhou City(Grant Nos.202102020389 and 202103030001)the Fund of Guangdong Provincial Key Laboratory of Information Photonics Technology(Grant No.2020B121201011)the National Natural Science Foundation of China(Grant Nos.11804058 and 12064027)。
文摘The thermoelectric properties of layered Mo_(2)AB_(2)(A=S,Se,Te;B=Cl,Br,I)materials are systematically investigated by first-principles approach.Soft transverse acoustic modes and direct Mo d–Mo d couplings give rise to strong anharmonicities and low lattice thermal conductivities.The double anions with distinctly different electronegativities of Mo_(2)AB_(2)monolayers can reduce the correlation between electron transport and phonon scattering,and further benefit much to their good thermoelectric properties.Thermoelectric properties of these Mo_(2)AB_(2)monolayers exhibit obvious anisotropies due to the direction-dependent chemical bondings and transport properties.Furthermore,their thermoelectric properties strongly depend on carrier type(n-type or p-type),carrier concentration and temperature.It is found that n-type Mo_(2)AB_(2)monolayers can be excellent thermoelectric materials with high electric conductivity,σ,and figures of merit,ZT.Choosing the types of A and B anions of Mo_(2)AB_(2)is an effective strategy to optimize their thermoelectric performance.These results provide rigorous understanding on thermoelectric properties of double-anions compounds and important guidance for achieving high thermoelectric performance in multi-anion compounds.
基金the National Natural Science Foundation of China(Grant No.11774416)the Fundamental Research Funds for the Central Universities(Grant Nos.2017XKZD08 and 2015XKMS081)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX202039)the Assistance Program for Future Outstanding Talents of China University of Mining and Technology(Grant No.2020WLJCRCZL063)。
文摘Nonisovalent(GaN)_(1-x)(ZnO)_(x)alloys are more technologically promising than their binary counterparts because of the abruptly reduced band gap.Unfortunately,the lack of two-dimensional(2D)configurations as well as complete stoichiometries hinders to further explore the thermal transport,thermoelectrics,and adsorption/permeation.We identify that multilayer(GaN)_(1-x)(ZnO)_(x)stabilize as wurtzite-like Pm-(GaN)_(3)(ZnO)_(1),Pmc2_(1)-(Ga N)_(1)(ZnO)_(1),P3m1-(GaN)_(1)(ZnO)_(2),and haeckelite C2/m-(GaN)_(1)(ZnO)_(3)via structural searches.P3m1-(GaN)_(1)(ZnO)_(2)shares the excellent thermoelectrics with the figure of merit ZT as high as 3.08 at 900 K for the p-type doping due to the ultralow lattice thermal conductivity,which mainly arises from the strong anharmonicity by the interlayer asymmetrical charge distributions.The p–d coupling is prohibited from the group theory in C2/m-(Ga N)_(1)(ZnO)_(3),which thereby results in the anomalous band structure versus Zn O composition.To unveil the adsorption/permeation of H^(+),Na^(+),and OH^(-)ions in AA-stacking configurations,the potential wells and barriers are explored from the Coulomb interaction and the ionic size.Our work is helpful in experimental fabrication of novel optoelectronic and thermoelectric devices by 2D(GaN)_(1-x)(ZnO)_(x)alloys.
基金Funding for this research is provided by the National Science Foundation,under award DMR-2136038Calculations were performed at the Center for Computational Research at SUNY Buffalo(http://hdl.handle.net/10477/79221).
文摘Quantum nuclear effects and anharmonicity impact a wide range of functional materials and their properties.One of the most powerful techniques to model these effects is the Stochastic Self-Consistent Harmonic Approximation(SSCHA).Unfortunately,the SSCHA is extremely computationally expensive,prohibiting its routine use.We propose a protocol that pairs machine learning interatomic potentials,which can be tailored for the system at hand via active learning,with the SSCHA.Our method leverages an upscaling procedure that allows for the treatment of supercells of up to thousands of atoms with practically minimal computational effort.The protocol is applied to PdCuH_(x)(x=0−2)compounds,chosen because previous experimental studies have reported superconducting critical temperatures,Tcs,as high as 17 K at ambient pressures in an unknown hydrogenated PdCu phase.We identify a P4/mmm PdCuH_(2)structure,which is shown to be dynamically stable only upon the inclusion of quantum fluctuations,as being a key contributor to the measured superconductivity.For this system,our methodology is able to reduce the computational expense for the SSCHA calculations by~96%.The proposed protocol opens the door towards the routine inclusion of quantum nuclear motion and anharmonicity in materials discovery.
基金support from the Croatian Science Foundation(Grant no.UIP-2019-04-6869 and UIP-2020-02-5675)from the European Regional Development Fund for the"Center of Excellence for Advanced Materials and Sensing Devices"(Grant No.KK.01.1.1.01.0001)+6 种基金as well as from the project"Podizanje znanstvene izvrsnosti Centra za napredne laserske tehnike(CALTboost)"financed by the European Union through the National Recovery and Resilience Plan 2021-2026(NRPP)J.P.B.,A.C.,and M.J.V.acknowledge computing time from a PRACE award granting access to Discoverer at SofiaTech in Bulgaria(OptoSpin project id.2020225411)EuroHPC(Extreme grant EHPC-EXT-2023E02-050)on Marenostrum5 at BSC,Spain,by the CECI(FRS-FNRS Belgium Grant No.2.5020.11)the Lucia Tier-1 of the Fédération Wallonie-Bruxelles(Walloon)support from ARC project DREAMS(G.A.21/25-11)funded by Federation Wallonie Bruxelles and ULiegethe EUSpecLab MSCA DTN network funded by EU Horizon Europe(G.A.101073486)the Excellence of Science project CONNECT(G.A.40007563)funded by FWO and FNRS.
文摘The Raman activeGmode in graphene exhibits a strong coupling to electrons,yet the comprehensive treatment of this interaction in the calculation of its temperature-dependent Raman spectrumremains incomplete.In this study,we calculate the temperature dependence of the G-mode frequency and linewidth,and successfully explain the experimental trend by accounting for the contributions arising from the first-order electron-phonon coupling,electron-mediated phonon-phonon coupling,and standard lattice anharmonicity.The generality of our approach enables its broad applicability to study phonon dynamics in materials where both electron-phonon coupling and anharmonicity are important.
基金supported by the National Natural Sci-ence Foundation of China(Nos.22373091,224B2305,and 22573099).
文摘In this work,we develop an extended dissipaton theory that generalizes the environmental couplings beyond the conventional linear and quadratic forms,enabling the treatment of ar-bitrary order of bath couplings.Ap-plying this theoretical framework to the condensed-phase non-Condon spectroscopy,we demonstrate the in-terplay of anharmonicity,non-Con-don and solvent effects on optical spectra,where the higher-order cou-plings arise from the anharmonicity of nuclear potential surface of the excited state.Precise simulations are carried out with high efficiency on linear absorption spectra involving the above mentioned correlated effects.We exhibit how an anharmonic potential modulates the vibronic feature,offering insights into the role of nonlinear environmental couplings in spectroscopic signatures and exemplifying the success of the extended dissipaton formalism as an exact and efficient method for higher-or-der bath couplings.
基金the National Natural Science Foundation of China(No.52072188)the Program for Science and Technology Innovation Team in Zhejiang(No.2021R01004)acknowledge the Institute of High Pressure Physics of Ningbo University for its computational resources。
文摘Pressure serves as a powerful approach to regulating the thermal conductivity of materials.By applying pressure,one can alter the lattice symmetry,atomic spacing,and phonon scattering mechanisms,thereby exerting a profound influence on thermal transport properties.SnS,sharing the same crystal structure as SnSe,has often been overlooked due to its higher lattice thermal conductivity.While extensive efforts have been dedicated to enhancing the power factor of SnS through doping,its thermal transport properties remain underexplored,limiting its potential as a thermoelectric material.In this study,we investigated the impact of pressure modulation on the thermoelectric performance of SnS.Remarkably,the application of negative pressure significantly enhanced its thermal transport characteristics,leading to a reduction in the lattice thermal conductivity(κL)along the axis to 0.23 W/(m·K)at 800 K,on par with that of SnSe.Despite the negligible improvement in carrier mobility under negative pressure,the electronic transport properties were preserved within an acceptable range.Most notably,a maximum ZT value of 2.7 was achieved along the axis at 800 K,marking a substantial advancement in the thermoelectric performance of n-type SnS.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12374008, 12022408, 12304013, 12374009, 12074138, 22131006, 52288102, and 52090024)the Interdisciplinary Integration and Innovation Project of JLU, Fundamental Research Funds for the Central Universities and the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT), open project from state key laboratory of superhard materials (No. 202408)+6 种基金College Student Innovation and Entrepreneurship Training Program (No. S202310183153)support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (Grant Agreement No. 802533)the Spanish Ministry of Science and Innovation (Grant No. PID2022142861NA-I00)the Department of Education, Universities and Research of the Eusko Jaurlaritza and the University of the Basque Country UPV/EHU (Grant No. IT1527-22)Simons Foundation through the Collaboration on New Frontiers in Superconductivity (Grant No. SFI-MPS-NFS-00006741-10)Y.-W.F. acknowledges the Extraordinary Grant of CSIC (No. 2025ICT122)the IKUR Strategy-High Performance Computing and Artificial Intelligence (HPC&AI) 2025-2026 of the Department of Science, Universities and Innovation of the Basque Government. Technical and human support provided by DIPC Supercomputing Center is gratefully acknowledged.
文摘Metal-stuffed B–C compounds with sodalite clathrate structure have captured increasing attention due to their predicted exceptional superconductivity above liquid nitrogen temperature at ambient pressure.However,by neglecting the quantum lattice anharmonicity,the existing studiesmay result in an incomplete understanding of such a lightweight system.Here,using state-of-the-art ab initio methods incorporating quantum effects and machine learning potentials,we revisit the properties of a series of XYB_(6)C_(6)clathrates where X and Y are metals.Our findings show that ionic quantum and anharmonic effects can harden the E_(g)and E_(u)vibrational modes,enabling the dynamical stability of 15 materials previously considered unstable in the harmonic approximation,including materials with previously unreported (XY)^(1+)state,which is demonstrated here to be crucial to reach high critical temperatures.Further calculations based on the anisotropic Migdal-Eliashberg equation demonstrate that the T_(c)values for KRbB_(6)C_(6)and RbB_(3)C_(3)among these stabilized compounds are 102 and 115 Kat 0 and 15 GPa,respectively,both being higher than T_(c)of 92 K of KPbB_(6)C_(6)at the anharmonic level.These record-high T_(c)values,surpassing liquid nitrogen temperatures,emphasize the importance of anharmonic effects in stabilizing B-C clathrates with large electron-phonon coupling strength and advancing the search for high-T_(c)superconductivity at(near)ambient pressure.
基金supported by the National Natural Science Foundation of China(Grant Nos.11335006,and 11405245)
文摘Thermal properties are essentially decided by atomic geometry and thus stress is the most direct way for manipulating. In this paper, we investigate stress modulation of thermal conductivity of graphene by molecular dynamics simulations and discuss the underlying microscopic mechanism. It is found that thermal conductivity of ftexural-free graphene increases with compression and decreases with strain, while thermal conductivity of flexural-included graphene decreases with both compression and strain. Such difference in thermal behavior originates from the changes in the anharmonicity of the interatomic potential, where the wrinkle scattering is responsible for the thermal conductivity diminishment in flexural-included graphene under strain. By comparing the results obtained from the Tersoff and AIREBO potentials, it is revealed that the degree of the symmetry of interatomic potential determines the thermal conductivity variation of graphene. Our results indicate that the symmetry of interatomic potential should be taken into careful consideration in constructing the lattice model of graphene.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12172047)Beijing Natural Science Foundation(Grant No.Z190011)Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Anharmonic lattice vibrations play pivotal roles in the thermal dynamics in condense matters and affect how the atoms interact and conduct heat.An in-depth understanding of the microscopic mechanism of phonon anharmonicity in condensed systems is critical for developing better functional and energy materials.In recent years,various novel behaviors in condense matters driven by phonon anharmonic effects were discovered,such as soft mode phase transition,negative thermal expansion(NTE),multiferroicity,ultralow thermal conductivity(κ),high thermal resistance,and high-temperature superconductivity.These properties have endowed anharmonicity with many promising applications and provided remarkable opportunities for developing“Anharmonicity Engineering”-regulating heat transport towards excellent performance in materials.In this work,we review the recent development of studies on phonon anharmonic effect and summarize its origin,mechanism,research methods,and applications.Besides,the remaining challenges,future trends,and prospects of phonon anharmonicity are also discussed.
基金supported by the 100 Talents Program of Sun Yat-sen University (Grant No. 76220-18841201)the National Natural Science Foundation of China (Grant No. 22022309)+2 种基金the Natural Science Foundation of Guangdong Province, China (Grant No. 2021A1515010024)the University of Macao (Grant Nos. SRG2019-00179-IAPME, and MYRG2020-00075IAPME)the Science and Technology Development Fund from Macao SAR (Grant No. FDCT-0163/2019/A3)。
文摘Two-dimensional(2D) van der Waals(vdW) materials have extraordinary thermal properties due to the effect of quantum confinement, making them promising for thermoelectric energy conversion and thermal management in microelectronic devices.In this review, the mechanism of phonon anharmonicity originating from three-and four-phonon interactions is derived. The phonon anharmonicity of 2D vdW materials, involving the Grüneisen parameter, phonon lifetime, and thermal conductivity, is summarized and derived in detail. The size-dependent thermal conductivity of representative 2D vdW materials is discussed experimentally and theoretically. This review will present fundamental and advanced knowledge on how to evaluate the phonon anharmonicity in 2D vdW materials, which will aid the design of new structures and materials for applications related to energy transfer and conversion.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174099,61922077,11874347,12088101,11991060U2230402)+3 种基金the National Key Research and Development Program of China(Grant Nos.2018YFB2200100,and 2020YFB1506400)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)the Beijing Science and Technology Committee(Grant No.Z181100005118003)supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y2021042)。
文摘Copper(Cu)-based materials(such as cuprates,Cu chalcogenides,and Cu halides)often exhibit unusual properties such as superconductivity,ultralow thermal conductivity,and superionicity.However,the electronic origin of these unusual behaviors remains elusive.In this study,we demonstrate that the high-lying occupied 3d orbital of Cu causes a strong s-d coupling with its unoccupied 4s state when local symmetry is reduced.This leads to strong phonon anharmonicity and is responsible for these intriguing properties.For example,during thermal transport,symmetry-controlled s-d coupling can substantially lower the lattice potential barrier,thereby enhancing the anharmonicity and scattering between phonons and ultimately significantly reducing lattice thermal conductivity.We confirmed this understanding with Raman spectra measurements,which demonstrated a remarkable red shift in the phonon vibrational frequency with an increase in the temperature of Cu-based semiconductors.Our study shows that the cause of phonon anharmonicity is related to the fundamental electronic structures,which can also explain other unusual physical properties of the Cu compounds.
文摘The hydrogen mean force from experimental neutron Compton profiles is derived using deep inelastic neutron scattering on amorphous and polycrystalline ice. The formalism of mean force is extended to probe its sensitivity to anharmonicity in the hydrogen-nucleus effective potential. The shape of the mean force for amorphous and polycrystalline ice is primarily determined by the anisotropy of the underlying quasi-harmonic effective potential. The data from amorphous ice show an additional curvature reflecting the more pronounced anharmonicity of the effective potential with respect to that of ice Ih.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104145 and 12374040)。
文摘The thermal switch plays a crucial role in regulating system temperature,protecting devices from overheating,and improving energy efficiency.Achieving a high thermal switching ratio is essential for its practical application.In this study,by utilizing first-principles calculations and semi-classical Boltzmann transport theory,it is found that hole doping with an experimentally achievable concentration of 1.83×10^(14)cm^(-2)can reduce the lattice thermal conductivity of monolayer MoS_(2) from 151.79 W·m^(-1)·K^(-1)to 12.19 W·m^(-1)·K^(-1),achieving a high thermal switching ratio of 12.5.The achieved switching ratio significantly surpasses previously reported values,including those achieved by extreme strain methods.This phenomenon mainly arises from the enhanced lattice anharmonicity,which is primarily contributed by the S atoms.These results indicate that hole doping is an effective method for tuning the lattice thermal conductivity of materials,and demonstrate that monolayer MoS_(2) is a potential candidate material for thermal switches.
基金supported by the National Natural Science Foundation of China(Grant Nos.12574028,U2330104,and 12074381)Guang-dong Basic and Applied Basic Research Foundation(Grant No.2024A1515010484)。
文摘Phonon quasiparticles and their anharmonic interactions govern heat transport in insulators.Accurate characterization of phonon frequencies and linewidths,especially beyond the quasiparticle approximation,is essential for understanding anharmonic effects and lattice thermal conductivity.Here,we investigate the anharmonic lattice dynamics and phonon transport in crystalline copper halides CuBiI_(4) using the self-consistent phonon theory,combined with the Wigner transport formalism and the quasi-harmonic Green–Kubo method.Results show that the three-phonon bubble self-energy substantially renormalizes the phonon dispersion,inducing strong modedependent broadening.Depending on the strength of the anharmonic scattering,phonons exhibit particle-like,wave-like,or overdamped transport characteristics,with broadened states contributing additional coherent thermal transport channels.We establish a consistent description of the overdamped phonon self-energy and advance the microscopic understanding of the strongly anharmonic phonon thermal transport in CuBiI_(4).Overdamped phonon modes significantly hinder the lattice thermal transport by reducing phonon lifetimes.However,the still well-defined phonon dispersions mitigate carrier scattering induced by the local structural disorder.Anisotropic electrical transport properties are obtained by considering polar and non-polar electroacoustic coupling and ionized impurity scattering mechanisms.Upon electron doping,the thermoelectric figure of merit of n-type CuBiI_(4) reaches 2.25 at 800 K.
基金supported by the Natural Science Foundation of Inner Mongolia(No.2020MS01023).
文摘The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.
基金supported by the Youth Innovation Promotion Association CAS (No. 2019298)Zhejiang Provincial High-level Talent Special Support Plan (No. 2020R52032)。
文摘Lattice thermal conductivity, κL, is a fundamental parameter for evaluating the performance of thermoelectric materials. However, the predicted value of κL based on the Debye dispersion model is often overestimated compared with the experimentally determined value.Many researchers have attempted to modify the theoretical model and have sought more reliable results. In this review,the recent progress in the study of phonon dispersion models is summarized and we propose that the lattice thermal conductivity can be most accurately determined by using the modified sinusoidal phonon dispersion model.Moreover, experimental methods that have the potential to reduce a thermoelectric material's κLare reviewed, for example, methods that generate standing waves or anharmonic lattice vibrations. A high concentration of standing waves and anharmonic lattice vibrations can effectively suppress excessive κL. Finally, this review presents the challenges of sinusoidal phonon dispersion when applied to real materials, which are often complicated and therefore time-consuming, especially when dealing with material defects.
基金V. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20773136 and No.30870591）, the National High-Tech Research and Development Program of China （No.2007AA02Z139）, and the Hundred Talent Fund of the Chinese Academy of Sciences.
文摘Changes of molecular structure and associated charge distributions, and changes of anharmonic vibrational parameters from DNA base monomers to the Watson-Crick base pairs, have been investigated at the density functional theory level. Through examination of the NH2, N H, and C=O stretching vibrational modes that are involved in the multiple H-bonds in the base pairs, sensitivity of their diagonal and off-diagonal anharmonicities, as well as anharmonic vibrational couplings, to the structure change are predicted. Our results reveal the intrinsic connection between the anharmonic vibrational potentials, H-bonding, and electrostatic interactions in DNA bases.
基金This work was supported by the Hundred Talent Fund of the Chinese Academy of Sciences, and also supported by the National Natural Science Foundation of China （No.21473212, No.20727001 and No.21573243）. The author thanks P. Yu and J. Zhao for their technical assistances.
文摘Vibrational and structural dynamics of two transition metal carbonyl complexes, Mn（CO）5Br and Re（CO）5Br were examined in DMSO, using ultrafast infrared pump-probe spectroscopy, steady-state linear infrared spectroscopy and quantum chemistry computations. Two car- bonyl stretching vibrational modes （a low-frequency A1 mode and two high-frequency degenerate E modes） were used as vibrational probes. Central metal effect on the CO bond order and force constant was responsible for a larger E-A1 frequency separation and a generally more red-shifted E and A1 peaks in the Re complex than in the Mn complex. A generally broader spectral width for the A1 mode than the E mode is believed to be partially due to vibrational lifetime effect. Vibrational mode-dependent diagonal anharmonicity was observed in transient infrared spectra, with a generally smaller anharmonicity found for the E mode in both the Mn and Re complexes.
