Quantitatively Analyzing Phonon Spectral Contribution of Thermal Conductivity Based on Non-Equilibrium Molecular Dynamics Simulation I: From Space Fourier Transform
Probing detailed spectral dependence of phonon transport properties in bulk materials is critical to improve the function and performance of structures and devices in a diverse spectrum of technologies. Currently, such information can only be provided by the phonon spectral energy density (SED) or equivalently time domain normal mode analysis (TDNMA) methods in the framework of equilibrium molecular dynamics simulation (EMD), but has not been realized in non-equilibrium molecular dynamics simulations (NEMD) so far. In this paper we generate a new scheme directly based on NEMD and lattice dynamics theory, called time domain direct decomposition method (TDDDM), to predict the phonon mode specific thermal conductivity. Two benchmark cases of Lennard-Jones (LJ) Argon and Stillinger-Weber (SW) Si are studied by TDDDM to characterize contributions of individual phonon modes to overall thermal conductivity and the results are compared with that predicted using SED and TDNMA. Excellent agreements are found for both cases, which confirm the validity of our TDDDM approach. The biggest advantage of TDDDM is that it can be used to investigate the size effect of individual phonon modes in NEMD simulations, which cannot be tackled by SED and TDNMA in EMD simulations currently. We found that the phonon modes with mean free path larger than the system size are truncated in NEMD and contribute little to the overall thermal conductivity. The TDDDM provides direct physical origin for the well-known strong size effects in thermal conductivity prediction by NEMD.
Separating electron and phonon thermal conductivity components is imperative for understanding the principle thermal transport mechanisms in metals and highly desirable in many applications. In this work, we predict the mode-dependent electron and phonon thermal conductivities of 18 different metals at room-temperature from first-principles. Our first-principles predictions, in general, agree well with experimental data. We find that the phonon thermal conductivity is in the range of 2 - 18 $W/mK$, which accounts for 1% - 40% of the total thermal conductivity. It is also found that the phonon …
The thermal conductivity of boron arsenide (BAs) is believed to be influenced by phonon scattering selection rules due to its special phonon dispersion. Compression of BAs leads to significant changes in phonon dispersion, which allows for a test of first principles theories for how phonon dispersion affects three- and four-phonon scattering rates. This study reports the thermal conductivity of BAs from 0 to 30 GPa. Thermal conductivity vs. pressure of BAs is measured by time-domain thermoreflectance with a diamond anvil cell. In stark contrast to what is typical for nonmetallic crystals, BAs …
Significant reduction of lattice thermal conductivity by electron-phonon interaction in silicon with high carrier concentrations: a first-principles study
The mechanisms causing the reduction in lattice thermal conductivity in highly P- and B-doped Si are looked into in detail. Scattering rates of phonons by point defects, as well as by electrons, are calculated from first principles. Lattice thermal conductivities are calculated considering these scattering mechanisms both individually and together. It is found that at low carrier concentrations and temperatures phonon scattering by electrons is dominant and can reproduce the experimental thermal conductivity reduction. However, at higher doping concentrations the scattering rates of phonons by…
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 d…
Declining the lattice thermal conductivity in graphene is essential for its thermoelectric applications. In high electron density systems, scatterings of phonons by electrons are no less than the phonon scatterings by other phonons. With the aid of first-principle calculations we examine the lattice thermal conductivity in graphene by inducing electron-phonon scattering externally. With experimentally tunable charge carrier density we find $\sim 50\%$ reduction of the lattice thermal conductivity at 200 K. The present study opens up new avenues for potential thermoelectric applications of grap…
Phonon scattering by electrons, or "phonon-electron scattering", has been recognized as a significant scattering channel for phonons in materials with high electron concentration, such as thermoelectrics and nanoelectronics, even at room temperature. Despite the abundant previous studies of phonon-electron scattering in different types of three-dimensional (3D) bulk materials, its impact on the phonon transport, and thus the heat transfer properties, of two-dimensional (2D) materials has not been understood. In this work, we apply ab initio methods to calculate the phonon-electron scattering r…
FourPhonon is a computational package that can calculate four-phonon scattering rates in crystals. It is built within ShengBTE framework, which is a well-recognized lattice thermal conductivity solver based on Boltzmann transport equation. An adaptive energy broadening scheme is implemented for the calculation of four-phonon scattering rates. In analogy with $thirdorder.py$ in ShengBTE, we also provide a separate python script, $Fourthorder.py$, to calculate fourth-order interatomic force-constants. The extension module preserves all the nice features of the well-recognized lattice thermal con…
Recent studies reveal that four-phonon scattering is generally important in determining thermal conductivities of solids. However, these studies have been focused on materials where thermal conductivity $κ$ is dominated by acoustic phonons, and the impact of four phonon scattering, although significant, is still generally smaller than three-phonon scattering. In this work, taking AlSb as example, we demonstrated that four-phonon scattering is even more critical to three-phonon scattering as it diminishes optical phonon thermal transport, and therefore significantly reduces the thermal conducti…
Uranium dioxide (UO$_2$), one of the most important nuclear fuels, can accumulate excess oxygen atoms as interstitial defects, which significantly impacts thermal properties. In this study, thermal conductivities and inelastic neutron scattering measurements on UO$_2$ and UO$_{2+x}$ (x=0.3, 0.4, 0.8, 0.11) were performed at low temperatures (2-300 K). The thermal conductivity of UO$_{2+x}$ is significantly suppressed compared to UO$_2$ except near the Néel temperature TN= 30.8 K, where it is independent of x. Phonon measurements demonstrate that the heat capacities and phonon group velocities …
Recently, Cd3As2 has attracted intensive research interest as an archetypical Dirac semimetal, hosting three-dimensional linear-dispersive electronic bands near the Fermi level. Previous studies have shown that single-crystalline Cd3As2 has an anomalously low lattice thermal conductivity, ranging from 0.3 W/mK to 0.7 W/mK at 300 K, which has been attributed to point defects. In this work, we combine first-principles lattice dynamics calculations and temperature-dependent high-resolution Raman spectroscopy of high-quality single-crystal thin films grown by molecular beam epitaxy to reveal the e…
In this work, we report thermal conductivity(k) of magnesium telluride (MgTe) with various crystallographic phases such as rocksalt, zincblende, wurtzite and nickel arsenic (NiAs) using density functional theory and Boltzmann transport equation. Our first principles calculations results show the low thermal conductivity of MgTe with kNiAs < krocksalt < kwurtzite < kzincblende. We systematically investigated the phonon group velocity, phonon scattering rate and mode contributed thermal conductivity of transverse acoustic (TA), longitudinal acoustic (LA) and optical phonons. Our first principles…
Metallic transition-metal nitrides (TMNs) are promising conductive ceramics for many applications, whose thermal transport is of great importance in device design. It is found metallic TiN and HfN hold anomalous thermal transport behaviors compared to common metals and nonmetallic TMNs. They have extremely large intrinsic phonon thermal conductivity mainly due to the large acoustic-optic phonon frequency gaps. The phonon thermal conductivity is reduced by two orders of magnitude as the phonon-isotope and phonon-electron scatterings are considered, which also induce the nontrivial temperature-i…
Knudsen-Controlled Switching of Thermal Conductivity Response by Targeted Phonon Excitation
Bauman Moscow State Technical University（莫斯科国立鲍曼技术大学）；National University of Defense Technology（国防科技大学）；Huazhong University of Science and Technology（华中科技大学）
This study presents the first-principles phonon calculations to understand the experimental thermal expansion ($α(T)$) and lattice thermal conductivity ($κ_{L}$) of CoSi at high temperature region. Phonon dispersion is computed using finite displacement method and supercell approach by taking the equilibrium crystal structures obtained from DFT. The calculation of $α(T)$ is done under quasi-harmonic approximation. The $κ_{L}$ is calculated using first-principle anharmonic lattice dynamics calculations under single-mode relaxation time approximation. Calculated $α(T)$ in the temperature range $…
Lattice thermal conductivity ($κ_{lat}$) of MgSiO$_3$ postperovskite (MgPPv) under the Earth's lower mantle high pressure-temperature conditions is studied using the phonon quasiparticle approach by combing \textit{ab initio} molecular dynamics and lattice dynamics simulations. Phonon lifetimes are extracted from the phonon quasiparticle calculations, and the phonon group velocities are computed from the anharmonic phonon dispersions, which in principle capture full anharmonicity. It is found that throughout the lowermost mantle, including the D" region, $κ_{lat}$ of MgPPv is ~25% larger than …
Impact of Rattlers on Thermal Conductivity of a Thermoelectric Clathrate: A First-Principles Study
利用第一性原理晶格动力学方法研究了晶格振动对Ba $_{8}$ Ga $_{16}$ Ge $_{30}$晶格热导率的影响.比较声子性质的填充和空的笼形物，我们表明，摇铃造成10倍的声子的弛豫时间减少，通过增加声子-声子散射概率。相反的共振散射的情况下，在弛豫时间的减少发生在一个很宽的频率范围内，这是至关重要的解释异常低的热导率的笼形物。我们还发现，振子对声子群速度的影响是次要的，因为声子色散的平坦化只发生在有限的相空间中的布里渊区。
A fundamental understanding of the phonon transport mechanism is important for optimizing the efficiency of thermoelectric devices. In this study, we investigate the thermal transport properties of the oxidized form of phosphorene called phosphorene oxide (PO) by solving phonon Boltzmann transport equation based on first-principles density functional theory. We reveal that PO exhibits a much lower thermal conductivity (2.42-7.08 W/mK, at 300 K) than its pristine counterpart as well as other two-dimensional materials. To comprehend the physical origin of such low thermal conductivity, we scruti…
We carry out a systematic study of the thermal conductivity of four single-layer transition metal dichalcogenides, MX$_2$ (M = Mo, W; X = S, Se) from first-principles by solving the Boltzmann Transport Equation (BTE). We compare three different theoretical frameworks to solve the BTE beyond the Relaxation Time Approximation (RTA), using the same set of interatomic force constants computed within density functional theory (DFT), finding that the RTA severely underpredicts the thermal conductivity of MS$_2$ materials. Calculations of the different phonon scattering relaxation times of the main c…
Motivated by the excellent electronic and optoelectronic properties of two-dimensional (2D) tin oxides, we systematically investigated the thermal conductivity of monolayer SnO and SnO2by the first-principles calculations. The room-temperature thermal conductivity of monolayer SnO and SnO2reaches 9.6 W/(mK) and 98.8 W/(mK), respectively. The size effect is much weaker for monolayer SnO than for monolayer SnO2, due to the coexistence of size dependent and independent component in the thermal conductivity of monolayer SnO. The large difference between the thermal conductivity of 2D tin oxides ca…
The phonon thermal transport properties of eight ternary intermetallic semiconductors are investigated by accounting for higher-order four-phonon scattering, phonon renormalization, and multi-channel thermal transport. The commonly used lowest-order theory, which accounts only for three-phonon scattering and without phonon renormalization, fails drastically for considered materials and underpredicts the thermal conductivity by up to a factor of two. The thermal conductivity decreases for three compounds and increases for five compounds with the application of higher-order corrections owing to …
Accessing the regime of coherent phonon propagation in nanostructures opens enormous possibilities to control the thermal conductivity in energy harvesting devices, phononic circuits, etc. In this paper we show that coherent phonons contribute substantially to the thermal conductivity of LaCoO3/SrTiO3 oxide superlattices, up to room temperature. We show that their contribution can be tuned through small variations of the superlattice periodicity, without changing the total superlattice thickness. Using this strategy, we tuned the thermal conductivity by 20% at room temperature. We also discuss…
The predictive modeling of lattice thermal conductivity is of fundamental importance for the understanding and design of materials for a wide range of applications. Two major approaches, namely molecular dynamics (MD) simulations and calculations solving approximately the Boltzmann transport equation (BTE), have been developed to compute the lattice thermal conductivity. We present a detailed direct comparison of these two approaches, using as prototypical cases MgO and PbTe. The comparison, carried out using empirical potentials, takes into account the effects of fourth order phonon scatterin…
Optical conductivity of rattling phonons in type-I clathrate Ba$_8$Ga$_{16}$Ge$_{30}$
利用太赫兹时域光谱技术在BaPDMATHABMM Ga $_{16}$ Ge $_{30}$中探测到一系列红外激活光学声子.在1.15和1.80 THz处具有最低峰的电导率谱被识别为所谓的摇铃声子，即，超大十面体笼中具有$T_{1u}$对称性的客体离子Ba的光学模式$^{2+}(2)$。从这些模式的光谱的温度依赖性是完全一致的计算的基础上的一维非谐势模型，随着温度的降低，形状变得不对称尖锐与软化的重量转移到较低的频率。这些温度依赖性是由非等间距能级非简谐声子光激发的玻色因子决定的，而不考虑相互作用的影响。
The thermal transport properties of biphenylene network (BPN), a novel sp2 -hybridized two-dimensional allotrope of carbon atoms recently realized in experiments [Fan et al., Science, 372 852-856 (2021)], are studied using the density functional theory-driven solution of the Boltzmann transport equation. The thermal transport in BPN is anisotropic and the obtained thermal conductivities are more than an order of magnitude lower than that in graphene, despite similar sp2-hybridized planar-structure of both allotropes. The lower thermal conductivity in BPN is found to originate from enhanced anh…
Thermoelectric technology is an alternate way to efficiently utilize the energy by converting waste heat into electricity. Thermoelectric requires material with low thermal conductivity to improves its thermoelectric performance. In this work, by solving Boltzmann transport equation based on first principles calculations, we report an ultra-low room temperature thermal conductivity of 2.08 Wm$^{-1}$K$^{-1}$ and 2.9 Wm$^{-1}$K$^{-1}$ along c-axis and a-axis respectively for pure MgPb$_2$Te. To explain this ultra-low thermal conductivity, we analyzed the elastic constants, phonon group velocity,…
I use first principles calculations to investigate the thermal conductivity of $β$-In$_2$O$_3$ and compare the results with that of $α$-Al$_2$O$_3$, $β$-Ga$_2$O$_3$, and KTaO$_3$. The calculated thermal conductivity of $β$-In$_2$O$_3$ agrees well with the experimental data obtain recently, which found that the low-temperature thermal conductivity in this material can reach values above 1000 W/mK. I find that the calculated thermal conductivity of $β$-Ga$_2$O$_3$ is larger than that of $β$-In$_2$O$_3$ at all temperatures, which implies that $β$-Ga$_2$O$_3$ should also exhibit high values of the…
