Unveiling Exceptional Thermoelectric Performance in Non-Layered X₂S₂ (X = K, Rb) via coexistence of flat band and high dispersion: Ultralow Lattice Thermal Conductivity and High Anisotropic ZT Values

Unveiling Exceptional Thermoelectric Performance in Non-Layered X₂S₂ (X = K, Rb) via coexistence of flat band and high dispersion: Ultralow Lattice Thermal Conductivity and High Anisotropic ZT Values | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 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Data may be preliminary. 23 May 2025 V1 Latest version Share on Unveiling Exceptional Thermoelectric Performance in Non-Layered X₂S₂ (X = K, Rb) via coexistence of flat band and high dispersion: Ultralow Lattice Thermal Conductivity and High Anisotropic ZT Values Authors : Lijun Ni , yinchang zhao , Yue Wang , Weisong Li , and zhenhong dai 0000-0001-7821-9932 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.174796931.15871590/v1 Published The Journal of Physical Chemistry C Version of record Peer review timeline 184 views 130 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract not-yet-known not-yet-known not-yet-known unknown The mechanical, thermal transport and thermoelectric characteristics of X2S2 (X = K, Rb) compounds are comprehensively investigated with the first-principles calculations, merging self-consistent phonon theory, Bubble theory, and Boltzmann transport equations. Our results reveal that the X2S2 materials exhibit good mechanical and thermal stability. Importantly, the strong lattice anharmonicity is found in X2S2. In addition to considering the quartic anharmonic renormalization of phonon frequency, we also introduce the Bubble term (which represents cubic anharmonic renormalization), thereby leading to an obvious phonon frequency shift. Thus, the accurate lattice thermal conductivity (κL) can be obtained by the SCP+Bubble-3ph4ph method, considering the temperature-driven phonon frequency shift and scatterings processes involving three-phonon (3ph) and four-phonon (4ph) scatterings. The calculated κL is found to be ultralow values with 0.84 (0.56) and 0.78 (0.49) WK-1m-1 along the a(b)- and c-axes at 300 K for K2S2 (Rb2S2), respectively. Moreover, the coexistence of high electronic dispersion band edges and electronic flat band edges along Γ to A direction causes the large power factor. Consequently, a high figure of merit (ZT) is achieved along the c-axis. The outstanding ZT peak values of n-type K2S2 (2.62) and n-type Rb2S2 (2.11) exceed 2 along the c-axis at 900 K, indicating their great potential for thermoelectric application. Remarkably, the ZT values display the significant anisotropy. These results emphatically reveal that the non-layered bulk n-type K2S2 material holds great promise for the development of thermoelectric devices with anisotropic properties in the future. Supplementary Material File (manuscript.docx) Download 21.24 MB Information & Authors Information Version history V1 Version 1 23 May 2025 Peer review timeline Published The Journal of Physical Chemistry C Version of Record 16 Sep 2025 Published Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords anomalous phonon transport density functional theory lattice thermal conductivity power factor thermoelectric performance Authors Affiliations Lijun Ni Yantai University View all articles by this author yinchang zhao Yantai University View all articles by this author Yue Wang Yantai University View all articles by this author Weisong Li China University of Mining and Technology View all articles by this author zhenhong dai 0000-0001-7821-9932 [email protected] Yantai University View all articles by this author Metrics & Citations Metrics Article Usage 184 views 130 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Lijun Ni, yinchang zhao, Yue Wang, et al. Unveiling Exceptional Thermoelectric Performance in Non-Layered X₂S₂ (X = K, Rb) via coexistence of flat band and high dispersion: Ultralow Lattice Thermal Conductivity and High Anisotropic ZT Values. Authorea . 23 May 2025. 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