Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investi...Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investigate the lattice dynamics of Cs_(2)AgInCl_(6)using first-principles calculations.By explicitly incorporating four-phonon scattering and wave-like phonon tunneling,we predict a k_(l)of 0.52 W·m^(-1)·K^(-1)with a remarkably weak temperature dependence(k_(l)∝T^(-0.31)),confirming the intrinsically glass-like ultralow k_(l)in Cs_(2)AgInCl_(6).Further analyses reveal that hierarchical chemical bonds,loosely bonded rattling atoms and a mixed crystalline-liquid state collectively induce strong anharmonicity manifested in flat phonon modes.These factors dominate the glass-like thermal transport component of k_(l).This work uncovers the underlying mechanisms governing the unusual thermal transport properties in lead-free HDPs and offers guiding principles for designing novel energy conversion technologies.展开更多
南方红壤丘陵区不同用材林下土壤侵蚀特征及其对有机碳(SOC)含量的影响与机制尚不明确。应用137Cs示踪技术,以桂北低山丘陵区的杂木林、马尾松林和桉树林为研究对象,研究不同林型和坡位下土壤侵蚀特征及其对SOC含量的影响。结果表明,土...南方红壤丘陵区不同用材林下土壤侵蚀特征及其对有机碳(SOC)含量的影响与机制尚不明确。应用137Cs示踪技术,以桂北低山丘陵区的杂木林、马尾松林和桉树林为研究对象,研究不同林型和坡位下土壤侵蚀特征及其对SOC含量的影响。结果表明,土壤侵蚀模数的范围为-3009.29—7472.95 t km^(-2)a^(-1),不同林型间表现为桉树林(4659.56 t km^(-2)a^(-1))>马尾松(938.99 t km^(-2)a^(-1))>杂木林(-1476.90 t km^(-2)a^(-1)),不同坡位为上坡(3416.71 t km^(-2)a^(-1))>中坡(621.80 t km^(-2)a^(-1))>下坡(83.14 t km^(-2)a^(-1))。与背景值相比,3个林地的上坡位均发生了土壤侵蚀,下坡位均发生了土壤沉积,桉树人工林的土壤侵蚀量较大。SOC和粘粒含量分别在不同林型和坡位上具有一致的分布规律,其平均值在不同林型间表现为桉树林<马尾松林<杂木林,不同坡位间表现为上坡<中坡<下坡。土壤侵蚀模数与SOC、粘粒含量均呈显著负相关,与粉粒含量呈显著正相关。结构方程模型表明,土壤侵蚀通过降低土壤粘粒含量从而减小SOC含量。在土壤侵蚀最大的上坡位,应注意防风固土措施的选择,如营造混交林。加强对人工林林下凋落物的保留与林下植被的恢复措施,以减少土壤侵蚀和增加土壤碳固存,充分发挥人工林在水土保持中的作用。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12204482),the Natural Science Foundation of Shanxi Province(Grant No.202403021221164)Higher education teaching reform and innovation project of Shanxi Province(Grant No.J20220480)the Natural Science Foundation of Hainan Province(Grant Nos.525MS080 and 225MS076).
文摘Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investigate the lattice dynamics of Cs_(2)AgInCl_(6)using first-principles calculations.By explicitly incorporating four-phonon scattering and wave-like phonon tunneling,we predict a k_(l)of 0.52 W·m^(-1)·K^(-1)with a remarkably weak temperature dependence(k_(l)∝T^(-0.31)),confirming the intrinsically glass-like ultralow k_(l)in Cs_(2)AgInCl_(6).Further analyses reveal that hierarchical chemical bonds,loosely bonded rattling atoms and a mixed crystalline-liquid state collectively induce strong anharmonicity manifested in flat phonon modes.These factors dominate the glass-like thermal transport component of k_(l).This work uncovers the underlying mechanisms governing the unusual thermal transport properties in lead-free HDPs and offers guiding principles for designing novel energy conversion technologies.
文摘南方红壤丘陵区不同用材林下土壤侵蚀特征及其对有机碳(SOC)含量的影响与机制尚不明确。应用137Cs示踪技术,以桂北低山丘陵区的杂木林、马尾松林和桉树林为研究对象,研究不同林型和坡位下土壤侵蚀特征及其对SOC含量的影响。结果表明,土壤侵蚀模数的范围为-3009.29—7472.95 t km^(-2)a^(-1),不同林型间表现为桉树林(4659.56 t km^(-2)a^(-1))>马尾松(938.99 t km^(-2)a^(-1))>杂木林(-1476.90 t km^(-2)a^(-1)),不同坡位为上坡(3416.71 t km^(-2)a^(-1))>中坡(621.80 t km^(-2)a^(-1))>下坡(83.14 t km^(-2)a^(-1))。与背景值相比,3个林地的上坡位均发生了土壤侵蚀,下坡位均发生了土壤沉积,桉树人工林的土壤侵蚀量较大。SOC和粘粒含量分别在不同林型和坡位上具有一致的分布规律,其平均值在不同林型间表现为桉树林<马尾松林<杂木林,不同坡位间表现为上坡<中坡<下坡。土壤侵蚀模数与SOC、粘粒含量均呈显著负相关,与粉粒含量呈显著正相关。结构方程模型表明,土壤侵蚀通过降低土壤粘粒含量从而减小SOC含量。在土壤侵蚀最大的上坡位,应注意防风固土措施的选择,如营造混交林。加强对人工林林下凋落物的保留与林下植被的恢复措施,以减少土壤侵蚀和增加土壤碳固存,充分发挥人工林在水土保持中的作用。
