Self-consistent Phonon Research Articles

Synergistic effect of lone-pair electron and atomic distortion in introducing anomalous phonon transport in layered PbXSeF (X= Cu, Ag) compounds with low lattice thermal conductivity

Using first-principles calculations, self-consistent phonon theory and Boltzmann transport theory, the crystal structure, phonon and electronic transport, and thermoelectric (TE) properties of PbXSeF (X = Cu, Ag) compounds are comprehensive explored in the current work. The heterogeneous bonding characteristics along the in-plane and out-of-plane directions lead to low lattice thermal conductivities in PbXSeF (X = Cu, Ag) compounds. The low lattice thermal conductivity is primarily attributed to strong anharmonicity caused by the lone-pair electrons of Pb. Notably, the PbCuSeF compound, despite the lighter mass in comparison with PbAgSeF, exhibits relatively lower lattice thermal conductivity. Such finding can be attributed to the distortion introduced by Cu atom, which leads to strong quartic anharmonicity, and thereby suppressing the heat-carrying phonons through the rattling-like behavior of Cu atom. The lone-pair electrons of Pb2+ and the heterogeneous bonding characteristics in PbXSeF (X = Cu, Ag) compounds contribute the multi-valley band degeneracy, resulting the decoupling of Seebeck coefficient and electrical conductivity with carrier concentration while generating in a high power factor. Our current work not only illustrates the fundamental insights into the low lattice thermal conductivity and related anomaly of layered PbXSeF (X = Cu, Ag) compounds based on the four-phonon scattering and multiple carrier scattering rates, but also highlights the anisotropic feature of electronic and thermal transport properties.

Excellent thermoelectric performance in alkali metal phosphides M3P (M = Na and K) with phonon-glass electron-crystal like behaviour.

Identifying ideal thermoelectric materials presents a formidable challenge due to the intricate coupling relationship between thermal conductivity and power factor. Here, based on first-principles calculations, along with self-consistent phonon theory and the Boltzmann transport equation, we theoretically investigate the thermoelectric properties of alkali metal phosphides M3P (M = Na and K). The evident 'avoided crossing' phenomenon indicates the phonon glass behavior of M3P (M = Na and K). Due to the strong lattice anharmonicity induced by alkali metal elements, accounting for quartic anharmonic corrections, the lattice thermal conductivities of Na3P and K3P at room temperature are merely 0.25 and 0.12 W m-1 K-1, respectively. Furthermore, the high degeneracy and 'pudding-mold-type' band structure lead to high p-type PF in M3P (M = Na and K). At 300 K, the p-type power factors (PF) of Na3P and K3P can reach 3.90 and 0.80 mW mK-2, respectively. The combination of ultralow κL and high PF leads to excellent thermoelectric figure of merit (ZT) values of 1.70 (3.38) and 1.18 (2.13) for p-type Na3P and K3P under optimal doping concentration at 300 K (500 K), respectively, surpassing traditional thermoelectric materials. These findings demonstrate that M3P (M = Na and K) exhibits behavior similar to phonon-glass electron crystals, thereby indicating a direction for the search for high-performance thermoelectric materials.

Machine Learning for Predicting Ultralow Thermal Conductivity and High ZT in Complex Thermoelectric Materials.

Efficient and precise calculations of thermal transport properties and figures of merit, alongside a deep comprehension of thermal transport mechanisms, are essential for the practical utilization of advanced thermoelectric materials. In this study, we explore the microscopic processes governing thermal transport in the distinguished crystalline material Tl9SbTe6 by integrating a unified thermal transport theory with machine learning-assisted self-consistent phonon calculations. Leveraging machine learning potentials, we expedite the analysis of phonon energy shifts, higher-order scattering mechanisms, and thermal conductivity arising from various contributing factors, such as population and coherence channels. Our finding unveils an exceptionally low thermal conductivity of 0.31 W m-1 K-1 at room temperature, a result that closely correlates with experimental observations. Notably, we observe that the off-diagonal terms of heat flux operators play a significant role in shaping the overall lattice thermal conductivity of Tl9SbTe6, where the ultralow thermal conductivity resembles that of glass due to limited group velocities. Furthermore, we achieve a maximum ZT value of 3.17 in the c-axis orientation for p-type Tl9SbTe6 at 600 K and an optimal ZT value of 2.26 in the a-axis and b-axis direction for n-type Tl9SbTe6 at 500 K. The crystalline Tl9SbTe6 not only showcases remarkable thermal insulation but also demonstrates impressive electrical properties owing to the dual-degeneracy phenomenon within its valence band. These results not only elucidate the underlying reasons for the exceptional thermoelectric performance of Tl9SbTe6 but also suggest potential avenues for further experimental exploration.

Excellent thermoelectric properties and significant anisotropy for filled-tetragonal NaZnAs caused by strong anharmonicity

We have theoretically investigated the transport properties of the filled-tetrahedral NaZnAs using first-principles calculations in combination with self-consistent phonon theory and the Boltzmann transport equation. The results show that the transport behavior of NaZnAs exhibits obvious anisotropy, and the influence of quartic anharmonicity on the lattice thermal conductivity cannot be neglected as shown by the thermal conductivity results obtained from different computational models. Both the increase in scattering rates(SRs) and the decrease in group velocity signify a strong anharmonicity. We further find that the special vibrational modes due to the weak bonding of Zn atoms are the main source of anharmonicity. We find that considering the bubble diagram for the phonon self-energy correction reduces the κL by up to 28.04% at 700 K, which favors the capture of large ZT values. In addition, The ZT value of NaZnAs can reach 3.07 at 700 K, which shows great potential for thermoelectric applications.

Hierarchical characterization of thermoelectric performance in copper-based chalcogenide CsCu3S2: Unveiling the role of anharmonic lattice dynamics

Fundamental understanding of anharmonic lattice dynamics and heat conductance physics in crystalline compounds is critical for the development of thermoelectric energy conversion devices. Herein, we thoroughly investigate the microscopic mechanisms of thermal transport in CsCu3S2 by coupling the self-consistent phonon (SCP) theory with the linearized Wigner transport equation (LWTE). We explicitly consider both phonon energy shifts and broadening arising from both cubic and quartic anharmonicities, as well as diagonal/non-diagonal terms of heat flux operators in thermal conductivity. Our findings show that the strong anharmonicity of CsCu3S2 primarily arises from the presence of p-d anti-bonding hybridization between Cu and S atoms, coupled with the random oscillations of Cs atoms. Notably, the competition between phonon hardening described by the loop diagram and softening induced by the bubble diagram significantly influences particle-like propagation, predominantly reflected in group velocity and energy-conservation rule. Additionally, the electrical transport properties are determined by employing the precise momentum relaxation-time approximation (MRTA). At high temperatures, the thermoelectric performance of p-type CsCu3S2 reaches its optimum theoretical value of 0.94 along the in-plane direction based on advanced phonon renormalization theory. In striking contrast, the harmonic approximation theory significantly overestimates the thermoelectric efficiency at the same temperatures, rendering it an impractical expectation. Conversely, the first-order renormalization approach leads to a serious underestimation of the thermoelectric properties due to the over-correction of phonon energy. Our study not only reveals the pivotal role of anharmonic lattice dynamics in accurately assessing thermoelectric properties but also underscores the potential thermoelectric applications for novel copper-based chalcogenides.

Compressive strain-induced enhancement of thermoelectric performance in lead-free halide double perovskites K2SnX6 (X = I, Br, Cl)

Exploring thermoelectric materials with high performance and low cost is of great importance in mitigating environmental and energy challenges. Here, we provide an atomistic insight into strain-induced enhancement of thermoelectric performance in potassium-based halide double perovskite K2SnX6 (X = I, Br, Cl) using first-principles calculations. To get reliable predictions for transport properties, we adopt advanced methods such as self-energy relaxation time approximation for electron transport and unified theory for lattice transport in combination with self-consistent phonon approach. Our calculations highlight a promising thermoelectric figure of merit ZT over 1.01 in K2SnI6 when applying a compressive strain of −6%, being tenfold larger than those in the uncompressed compounds, suggesting that compressing is an effective way to enhance the thermoelectric performance of halide double perovskites.

Comparison of the excellent thermoelectric properties of the half-Heusler compounds RbMgSb with a host-guest structure and LiMgSb

In this work, we systematically studied the thermoelectric (TE) transport properties of the half-Heusler compounds AMgSb (A = Li, Rb) based on an incorporation of first-principles calculations with self-consistent phonon theory and Boltzmann transport equations. We noted significant changes in the vibrational behavior of alkali metal atoms with a substantial increase in atomic mass. This alteration led to the formation of a host-guest structure in RbMgSb. In contrast, the stronger harmonic vibrations in LiMgSb results in it maintaining a Half-Heusler structure, without the pronounced anharmonicity found in RbMgSb. The calculation results reveal that RbMgSb has ultra-low lattice thermal conductivity κL, which is ten times lower than LiMgSb. We show that rattlers cause tenfold reductions in the thermal conductivity by increasing the phonon–phonon scattering probability, occurred in a wide frequency range. In addition, after careful consideration of multiple scattering mechanisms, the multiple valleys, high dispersion, flat band edges and band asymmetry near the Fermi level give both materials excellent electron transport properties. At the same time, LiMgSb itself already has a very low electron thermal conductivity κe, but the κe of RbMgSb is ten times smaller than that. As a consequence, remarkable ZT values of 2.51 and 3.45 at 900 K are captured in n-type LiMgSb and p-type RbMgSb, respectively. These findings reveal the promising potential of AMgSb in TE applications.

Motorized chain models of the ideal chromosome

An array of motor proteins consumes chemical energy in setting up the architectures of chromosomes. Here, we explore how the structure of ideal polymer chains is influenced by two classes of motors. The first class which we call "swimming motors" acts to propel the chromatin fiber through three-dimensional space. They represent a caricature of motors such as RNA polymerases. Previously, they have often been described by adding a persistent flow onto Brownian diffusion of the chain. The second class of motors, which we call "grappling motors" caricatures the loop extrusion processes in which segments of chromatin fibers some distance apart are brought together. We analyze these models using a self-consistent variational phonon approximation to a many-body Master equation incorporating motor activities. We show that whether the swimming motors lead to contraction or expansion depends on the susceptibility of the motors, that is, how their activity depends on the forces they must exert. Grappling motors in contrast to swimming motors lead to long-ranged correlations that resemble those first suggested for fractal globules and that are consistent with the effective interactions inferred by energy landscape analyses of Hi-C data on the interphase chromosome.

Ultralow thermal conductivity and high thermoelectric performance induced by dimensionality reduction in chain-like compounds X2PtSe2 (X=K, rb)

Balancing low lattice thermal conductivity (κL) with a high power factor is a major challenge in the research of thermoelectric (TE) materials. In this paper, we report on a class of chain-like compounds, X2PtSe2(X = K, Rb), characterized by strong lattice anharmonicity, weak bonds, and low phonon group velocities. Using first-principles calculations in conjunction with self-consistent phonon theory and the Boltzmann transport equation, we systematically investigate the thermal and electrical transport properties of X2PtSe2(X = K, Rb). At room temperature, the κL of K2PtSe2 and Rb2PtSe2 in the direction perpendicular to the Pt–Se chains is only 0.15 and 0.10 Wm−1K−1, respectively. Additionally, due to the low-dimensional nature of the Pt–Se chains, these compounds exhibit a ‘pudding-mold type’ band structure, contributing to a TE power factor. At 300K, under n-type doping, K2PtSe2 and Rb2PtSe2 achieve TE figures of merit (ZT) values of 1.66 and 1.67, respectively, in the direction perpendicular to the Pt–Se chains. At 500K, the ZT value of Rb2PtSe2 approaches 4, far surpassing traditional TE materials. These results indicate that the chain-like compounds X2PtSe2(X = K, Rb) exhibit excellent TE performance, achieving energy conversion efficiencies comparable to commercial transducer devices.

Terahertz electric-field-driven dynamical multiferroicity in SrTiO3

The emergence of collective order in matter is among the most fundamental and intriguing phenomena in physics. In recent years, the dynamical control and creation of novel ordered states of matter not accessible in thermodynamic equilibrium is receiving much attention1–6. The theoretical concept of dynamical multiferroicity has been introduced to describe the emergence of magnetization due to time-dependent electric polarization in non-ferromagnetic materials7,8. In simple terms, the coherent rotating motion of the ions in a crystal induces a magnetic moment along the axis of rotation. Here we provide experimental evidence of room-temperature magnetization in the archetypal paraelectric perovskite SrTiO3 due to this mechanism. We resonantly drive the infrared-active soft phonon mode with an intense circularly polarized terahertz electric field and detect the time-resolved magneto-optical Kerr effect. A simple model, which includes two coupled nonlinear oscillators whose forces and couplings are derived with ab initio calculations using self-consistent phonon theory at a finite temperature9, reproduces qualitatively our experimental observations. A quantitatively correct magnitude was obtained for the effect by also considering the phonon analogue of the reciprocal of the Einstein–de Haas effect, which is also called the Barnett effect, in which the total angular momentum from the phonon order is transferred to the electronic one. Our findings show a new path for the control of magnetism, for example, for ultrafast magnetic switches, by coherently controlling the lattice vibrations with light.

Anomalous thermal conductivity in 2D silica nanocages of immobilizing noble gas atom

Noble gas atoms such as Kr and Xe are byproducts of nuclear fission in nuclear plants. How to trap and confine these volatile even radioactive gases is particularly challenging. Recent studies have shown that they can be trapped in nanocages of ultrathin silica. Here, we exhibit with self-consistent phonon theory and four-phonon (4ph) scattering where the adsorption of noble gases results in an anomalous increase in lattice thermal conductivity (κL), while the presence of Cu atoms doping leads to a reduction in κL. We trace this behavior in host–guest 2D silica to an interplay of tensile strain, rattling phonon modes, and redistribution of electrons. We also find that 4ph scatterings play indispensable roles in κL of 2D silica. Our work illustrates the microscopic heat transfer mechanism in 2D silica nanocages with the immobilization of noble gas atoms and inspires further exploring materials with the kagome and glasslike κL.

Unravelling ultralow thermal conductivity in perovskite Cs2AgBiBr6: dominant wave-like phonon tunnelling and strong anharmonicity

Understanding the lattice dynamics and heat transport physics in the lead-free halide double perovskites remains an outstanding challenge due to their lattice dynamical instability and strong anharmonicity. In this work, we investigate the microscopic mechanisms of anharmonic lattice dynamics and thermal transport in lead-free halide double perovskite Cs2AgBiBr6 from first principles. We combine self-consistent phonon calculations with bubble diagram correction and a unified theory of lattice thermal transport that considers both the particle-like phonon propagation and wave-like tunnelling of phonons. An ultra-low thermal conductivity at room temperature (~0.21 Wm−1K−1) is predicted with weak temperature dependence( ~ T−0.34), in sharp contrast to the conventional ~T−1 dependence. Particularly, the vibrational properties of Cs2AgBiBr6 are featured by strong anharmonicity and wave-like tunnelling of phonons. Anharmonic phonon renormalization from both the cubic and quartic anharmonicities are found essential in precisely predicting the phase transition temperature in Cs2AgBiBr6 while the negative phonon energy shifts induced by cubic anharmonicity has a significant influence on particle-like phonon propagation. Further, the contribution of the wave-like tunnelling to the total thermal conductivity surpasses that of the particle-like propagation above around 310 K, indicating the breakdown of the phonon gas picture conventionally used in the Peierls-Boltzmann Transport Equation. Importantly, further including four-phonon scatterings is required in achieving the dominance of wave-like tunnelling, as compared to the dominant particle-like propagation channel when considering only three-phonon scatterings. Our work highlights the importance of lattice anharmonicity and wave-like tunnelling of phonons in the thermal transport in lead-free halide double perovskites.

Self-consistent phonon calculations and quartic anharmonic lattice thermal conductivity in 2D InS monolayer

Low lattice thermal conductivity (κl) is a crucial factor for higher figure-of merit and hence the efficiency of thermoelectric generators. There are several reports on intrinsically low κl values in two-dimensional (2D) van der Waals materials using density functional theory and molecular dynamics simulations. In general, phonon dispersions are studied at absolute zero temperature using the finite-displacement approach within harmonic approximations. In addition, the κlis calculated using the third-order cubic interatomic force constants (IFCs) by solving the Boltzmann transport equation for phonons. In these calculations, we use quartic IFCs to solve self-consistent phonon equations to obtain dynamical dispersion relations at a finite temperature of 300 K using finite-temperature Green’s function for Bosonic systems in 2D indium sulfide (InS) monolayer. The cubic and quartic IFCs are calculated using machine learning algorithms, namely, the ordinary least square fitting and the least absolute shrinkage and selection operator. It was found that there is a lowering of the renormalized anharmonic phonon frequencies in the dispersion relations at 300 K upon the inclusion of quartic IFCs and anharmonic terms in the case of the InS monolayer. Thus, the κlvalue is reduced to 0.6 W/mK as compared to 0.9 W/mK obtained using cubic IFCs.

Thermal conductivity study of 2D Si4C8 materials by anharmonic phonon renormalization.

In this investigation, we employed the anharmonic phonon renormalization method to analyze the thermal conductivity of two-dimensional (2D) carbon materials, while also examining the influence of quartic (fourth-order) scattering on heat transport within this class of materials. Our study centered on a representative silicon-carbon (Si-C) 2D system, Si4C8. Notably, conventional Boltzmann transport equation (BTE) calculations with harmonic phonons are inadequate for estimating the thermal conductivity of these materials due to the emergence of imaginary frequencies. Consequently, to elucidate the primary contributors to its heat transport, we employed an integrated yet novel computational framework rooted in a first-principles methodology. This approach combines self-consistent phonon (SCP) theory and the BTE to scrutinize the thermal conduction behavior; the BTE is resolved in conjunction with SCP theory to comprehensively address the quartic anharmonic effects, encompassing both four-phonon (4ph) scatterings and the temperature-induced shift of phonon frequencies. Based on the calculation results, it is evident that the meticulous incorporation of anharmonicity renormalization is pivotal for precise evaluation of the thermal conductivity of 2D Si4C8 and establishing coherent temperature dependency. Through this comprehensive examination, we aim to establish a systematic methodology for investigating the thermal transport mechanisms of 2D Si-C phases with similar bonding networks, offering insights into the intricate relationships between their structural, mechanical, electronic, and thermal properties.

Intrinsic ultralow lattice thermal conductivity in lead-free halide perovskites Cs3Bi2X9 (X = Br, I).

Lead-free halide perovskites have recently garnered significant attention due to their rich structural diversity and exceptionally ultralow lattice thermal conductivity (κL). Here, we employ first-principles calculations in conjunction with self-consistent phonon theory and Boltzmann transport equations to investigate the crystal structure, electronic structure, mechanical properties, and κLs of two typical vacancy-ordered halide perovskites, denoted with the general formula Cs3Bi2X9 (X = Br, I). Ultralow κLs of 0.401 and 0.262 W mK-1 at 300 K are predicted for Cs3Bi2Br9 and Cs3Bi2I9, respectively. Our findings reveal that the ultralow κLs are mainly associated with the Cs rattling-like motion, vibrations of halide polyhedral frameworks, and strong scattering in the acoustic and low-frequency optical phonon branches. The structural analysis indicates that these phonon dynamic properties are closely relevant to the bonding hierarchy. The presence of the extended Bi-X antibonding states at the valence band maximum contributes to the soft elastic lattice and low phonon group velocities. Compared to Cs3Bi2Br9, the face-sharing feature and weaker bond strength in Cs3Bi2I9 lead to a softer elasticity modulus and stronger anharmonicity. Additionally, we demonstrate the presence of wave-like κC in Cs3Bi2X9 by evaluating the coherent contribution. Our work provides the physical microscopic mechanisms of the wave-like κC in two typical lead-free halide perovskites, which are beneficial to designing intrinsic materials with the feature of ultralow κL.

Study on lattice dynamics and thermal conductivity of fluorite AF2 (A = Ca, Sr, Ba) based on first principles calculations.

Fluorite materials have received particular attention in electron optics due to their favorable optical properties. However, further exploration of these materials in the thermoelectric (TE) field is hampered by the lack of studies on their lattice thermal transport properties. In this work, we use first-principles calculations, combined with self-consistent phonon theory, compressive sensing lattice dynamics and the Boltzmann transport equation, to study the microscopic mechanism of lattice thermal transport properties in AF2 (A = Ca, Sr, Ba) with a fluorite structure. We investigate the effects of three-phonon and four-phonon scattering and quartic anharmonic renormalization of phonon frequencies on this system. The results show that the bonding strength of atoms A (Ca, Sr, and Ba) plays an important role in the thermal transport process, and the third-order anharmonicity also plays an important role in this system. Meanwhile, the role of the quartic anharmonicity cannot be ignored. Our findings not only fill in the gaps in the study of lattice thermal transport of fluorite materials, but also deepen the comprehensive understanding of the high κL value of fluorite materials.

Lattice Thermal Conductivity in XMg2Sb2(X = Ca or Mg) Compounds: Temperature and High-Order Anharmonicity Effect

The binary compound Mg3Sb2 (also written as MgMg2Sb2) exhibits a much lower lattice thermal conductivity (κL) than its ternary analog CaMg2Sb2, despite its relatively low mass density and simple crystalline structure. Here, we perform a comparative first-principles study of the lattice dynamics in MgMg2Sb2 and CaMg2Sb2 based on the density functional theory, together with the self-consistent phonon theory and the Boltzmann transport theory. We show that the modest anharmonicity of CaMg2Sb2 renders the three-phonon processes dominant, and the temperature dependence of κL approximately follows the T−1 relationship. In contrast, the strong quartic anharmonicity of MgMg2Sb2 leads to the ultralow κL and weak temperature dependence, in agreement with the experimental observations. A comprehensive analysis reveals that the κLs in the two compounds are mainly carried by the acoustic phonons associated with the Sb atoms, and the different behaviors of κL result from the chemical bond changes around Sb atoms, which bond more covalently with the Mg atoms than the Ca atoms and thus lead to high-order anharmonicity in MgMg2Sb2. These results give us insights into the understanding of the anomalous thermal transport in thermoelectric materials.

Room temperature high thermoelectric performance of Bi-based full-Heusler compounds CsxRb[formula omitted]Bi with strong anharmonicity

Bismuth-based compounds have been identified as a class of promising candidates for the realization of high-performance thermoelectrics, derived from their exceptional electrical conductivity and intrinsic low lattice thermal conductivity κL. Here, we employed first-principles calculations, self-consistent phonon theory, and compressive sensing technique in conjunction with the Boltzmann transport equation to investigate the anharmonic thermoelectric properties of full-heusler bismuth compounds CsxRb3−xBi. As the Cs content increases, the κL of CsxRb3−xBi decreases due to impurity scattering effects, and then increases. Among them, at 300 K, Rb3Bi has the largest κL of 0.69 Wm−1K−1, while Cs2RbBi has the smallest κL of 0.45 Wm−1K−1, both of which are lower than the κL of traditional bismuth-based thermoelectric materials. The ultralow κL originates from the strong lattice anharmonicity. In addition, the coexistence of high dispersion and flat band edges leads to high thermoelectric power factor at optimal doping concentration. As a result, the largest thermoelectric figure of merit ZT values of 2.59 (4.19) at 300 (500) K were obtained for CsRb2Bi at optimal hole doping level. These findings suggest that CsxRb3−xBi compounds are superior for thermal management and thermoelectric applications.

Exploring anharmonic lattice dynamics and dielectric relations in niobate perovskites from first-principles self-consistent phonon calculations

Group I niobates (KNbO3 and NaNbO3) are promising lead-free alternatives for high-performance energy storage applications. Despite their potential, their complex phase transitions arising from temperature-dependent phonon softening and anharmonic effects on dielectric properties remain poorly explored. In this study, we employ density-functional theory (DFT) and self-consistent phonon (SCP) calculations to investigate finite-temperature phonons in cubic niobate perovskites. To include explicit anharmonic vibrational effects, SCP frequencies are shifted by the bubble self-energy correction within the quasiparticle (QP) approximation, providing precise descriptions of phonon softening in these strongly anharmonic solids. We further calculate the static dielectric constant of KNbO3 and NaNbO3 as a function of temperature using the Lyddane-Sachs-Teller (LST) relation and QP-corrected phonon dispersions. Our theoretical results align with experimental data, offering reliable temperature-dependent phonon dispersions while considering anharmonic self-energies and thermal expansion effects, enhancing our understanding of the complex relations between lattice vibrations and phase transitions in these anharmonic oxides.

The filled tetrahedral compound NaZnP with strong quartic anharmonicity and good thermoelectric properties

Based on first-principles calculations, self-consistent phonon (SCP) theory, and the Boltzmann transport equation, we investigate the thermal transport and thermoelectric properties of the Nowotny-Juza filled tetrahedral compound NaZnP. The effects of anharmonic phonon renormalization and four-phonon scattering on the heat transport of NaZnP are also considered. The weak binding and rattling-like vibrational behavior of Na atoms lead to strong lattice anharmonicity, and the results show that NaZnP has low lattice thermal conductivity. Furthermore, the coexistence of high dispersion and high degeneracy of valence band maxima leads to high power factor under p-type doping. The combination of low lattice thermal conductivity and good electrical transport properties results in high thermoelectric performance. This indicates that NaZnP is a promising p-type high-temperature thermoelectric material.