近年來，無鉛鹵化物雙鈣鈦礦由于其環(huán)境友好性以及穩(wěn)定性，在光電光伏領(lǐng)域得到了極大的關(guān)注。同時，由于其強非簡諧性可能引起超低熱導(dǎo)率，該材料在熱電領(lǐng)域也引起了極大的關(guān)注。然而，無鉛鹵化物雙鈣鈦礦的熱力學性質(zhì)具有強烈的溫度依賴性，導(dǎo)致傳統(tǒng)的晶格動力學和導(dǎo)熱模型難以適用。

為解決該問題，香港科技大學機械與航天航空工程系黃寶陵教授團隊、山東高等技術(shù)研究院郭瑞強教授團隊以及美國達特茅斯學院Geoffroy Hautier 教授團隊合作，提出了一種綜合考慮多種因素的導(dǎo)熱模型，該模型不僅精確考慮了有限溫度對材料熱力學性能的影響，而且在傳統(tǒng)導(dǎo)熱模型的基礎(chǔ)上增加了額外的導(dǎo)熱通道，從而能夠精準預(yù)測無鉛鹵化物雙鈣鈦礦的熱導(dǎo)率，揭示其導(dǎo)熱機理。

該研究通過綜合考慮多聲子溫度效應(yīng)，額外聲子熱傳輸通道以及四聲子相互作用揭示了Cs₂AgBiBr₆的導(dǎo)熱機理，發(fā)現(xiàn)了類波性聲子隧穿在其導(dǎo)熱過程中的主導(dǎo)作用。

Fig. 3 Thermal transport models, theoretically predicted and experimentally measured thermal conductivity.

作者不僅揭示了無鉛鹵化物雙鈣鈦礦Cs₂AgBiBr₆的導(dǎo)熱機理，還準確預(yù)測了其相變溫度，發(fā)現(xiàn)了三聲子相互作用對準確預(yù)測相變溫度的重要性。此外，鑒于雙鈣鈦礦熱力學性質(zhì)的強溫度依賴性，四聲子相互作用成為了一個關(guān)鍵因素，其納入考量導(dǎo)致了傳統(tǒng)導(dǎo)熱模型的失效。

該研究揭示了晶格的非簡諧性和類波性聲子隧穿對無鉛鹵化物雙鈣鈦礦熱輸運的重要影響。相關(guān)論文近期發(fā)布于npj?Computational Materials?10:?30?(2024)。手機閱讀原文，請點擊本文底部左下角“閱讀原文”，進入后亦可下載全文PDF文件。

Editorial Summary

In recent years, lead-free halide double perovskites have gained a lot of attention in the field of solar energy due to their environmental friendliness and stability. Additionally, their potential for extremely low thermal conductivity has sparked interest in the field of thermoelectrics. However, their strong temperature-dependent thermal properties make traditional lattice dynamics and heat transfer prediction models ineffective. This study introduces a heat transfer prediction model that integrates multiple factors. This model not only accurately considers the influence of finite temperatures on the thermal properties of double perovskite materials but also adds extra heat transfer pathways beyond traditional models. This allows for precise predictions and revelations about the heat transfer mechanisms of lead-free halide double perovskites.?

The?Professor Huang Baoling’s research team from the Department of Mechanical and Aerospace Engineering at the Hong Kong University of Science and Technology, Professor Guo Ruiqiang’s team from the Shandong Advanced Academy, and Professor Geoffroy Hautier’s team from Dartmouth College in the United States, comprehensively considered the effects of multi-phonon temperature, additional phonon heat transfer pathways, and four-phonon interaction processes. This revealed the heat transfer mechanisms of lead-free halide double perovskite Cs2AgBiBr6 and identified new additional phonon transfer pathways that dominate the heat transfer process. Apart from accurately revealing the heat transfer mechanisms of lead-free halide double perovskite Cs2AgBiBr6, the study also accurately predicted the phase transition temperature of double perovskite Cs2AgBiBr6. It emphasized the importance of three-phonon particle interactions for accurate phase transition temperature predictions. Additionally, considering the strong temperature dependence of double perovskites, four-phonon particle interactions are indispensable, and their involvement renders traditional heat transfer models ineffective. The research underscores the significance of lattice anharmonicity (temperature effects) and phonon wave-like tunnelling heat transfer pathways in the thermal transfer mechanism of lead-free halide double perovskite Cs2AgBiBr6. Thisarticle was recently?published in?npj?Computational Materials?10:?30?(2024).

原文Abstract及其翻譯

Unravelling ultralow thermal conductivity in perovskite Cs₂AgBiBr₆: dominant wave-like phonon tunnelling and strong anharmonicity?(揭示Cs₂AgBiBr₆鈣鈦礦的超低熱導(dǎo)率：類波性聲子隧穿的主導(dǎo)作用和強烈的非簡諧性)

Jiongzhi Zheng,?Changpeng Lin,?Chongjia Lin,?Geoffroy Hautier,?Ruiqiang Guo?&?Baoling Huang?

Abstract?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.

摘要無鉛鹵化物雙鈣鈦礦結(jié)構(gòu)的晶格不穩(wěn)定性和強非簡諧性導(dǎo)致其晶格動力學和導(dǎo)熱機理的理解仍然面臨極大的挑戰(zhàn)。本研究基于第一性原理計算，深入研究了無鉛鹵化物雙鈣鈦礦Cs₂AgBiBr₆的非簡諧晶格動力學及其熱輸運微觀機理。我們采用了帶bubble修正的自洽計算對聲子進行有限溫度重整，并結(jié)合統(tǒng)一熱傳導(dǎo)模型（考慮了類粒子性聲子傳播通道和類波性聲子隧穿傳播通道）來預(yù)測熱導(dǎo)率。在室溫下，模型預(yù)測Cs₂AgBiBr₆具有超低熱導(dǎo)率（約為0.21 Wm^?1K^?1），并呈現(xiàn)出極弱的溫度依賴性（?~?T^?0.34），與傳統(tǒng)的?~?T^?1依賴性形成鮮明對比。值得注意的是，Cs₂AgBiBr₆的表現(xiàn)出強烈的非簡諧性和類波性聲子隧穿特性。發(fā)現(xiàn)準確預(yù)測Cs₂AgBiBr₆的相變溫必須同時考慮三次和四次非諧聲子引起的重整，其中立方非諧性引起的負聲子能量偏移對類粒子的聲子傳播產(chǎn)生了顯著的影響。此外，當溫度達到310 K左右時，聲子隧穿的貢獻超越了類粒子聲子傳播，導(dǎo)致了Peierls-Boltzmann輸運方程中傳統(tǒng)的聲子氣模型失效。更重要的是，僅考慮三聲子散射時，粒子性傳播通道占主導(dǎo)；進一步考慮四聲子散射后，類波性聲子隧穿效應(yīng)成為主導(dǎo)。該研究揭示了晶格的強非簡諧性和類波性聲子隧穿對無鉛鹵化物雙鈣鈦礦熱輸運的重要影響。