We obtained a new material called monolayer 1T-Ag₆S₂ by replacing metal atoms in 1T phase transition-metal dichalcogenide sulfides (TMDs) with octahedral Ag₆ clusters. Subsequently, the thermoelectric transport properties of monolayer 1T-Ag₆S₂ were systematically investigated using first-principles calculations and the generalized gradient approximation (GGA-PBE) exchange correlation functional. The findings demonstrate that monolayer 1T-Ag₆S₂ displays characteristics of a wide-bandgap semiconductor, with a bandgap of 2.48 eV. Notably, the incorporation of Ag₆ clusters disrupts the structural symmetry, effectively enhancing the electronic structure and phonon properties of the material. Due to the flat valence band near the Fermi level, the extended relaxation time of the hole results in a greater effective mass compared to the electron, leading to a significant increase in the Seebeck coefficient. Under optimal doping conditions, the power factor of monolayer 1T-Ag₆S₂ can achieve 14.9 mW/mK² at 500 K. The intricate crystal structure induces phonon path bending, reduces the overall frequency of phonon vibrations (<10 THz), and causes hybridization of low-frequency optical and acoustic branches, resulting in remarkably low lattice thermal conductivity (0.20 and 0.17 W/mK along the x and y axes at 500 K, respectively). The monolayer 1T-Ag₆S₂ demonstrates a remarkably high figure of merit ZT of 3.14 (3.15) on the x (y) axis at 500 K, significantly higher than those of conventional TMD materials. Such excellent thermoelectric properties suggest that monolayer 1T-Ag₆S₂ is a promising thermoelectric (TE) material. Our work reveals the deep mechanism of cluster substitution to optimize the thermoelectric properties of materials and provides a useful reference for subsequent research.

中文翻译：

---

具有优异热电性能的单层1T-Ag6S2

_{我们通过用八面体Ag 6}簇取代1T相过渡金属二硫属化物硫化物（TMD）中的金属原子，获得了一种称为单层1T-Ag ₆ S ₂的新材料。随后，利用第一原理计算和广义梯度近似（GGA-PBE）交换相关函数系统地研究了单层1T-Ag ₆ S ₂的热电输运特性。研究结果表明，单层1T-Ag ₆ S ₂显示出宽带隙半导体的特性，带隙为2.48 eV。值得注意的是，Ag ₆簇的掺入破坏了结构对称性，有效增强了材料的电子结构和声子性能。由于费米能级附近的平坦价带，与电子相比，空穴的弛豫时间延长导致有效质量更大，从而导致塞贝克系数显着增加。在最佳掺杂条件下，单层1T-Ag ₆ S ₂的功率因数在500 K时可以达到14.9 mW/mK ²。复杂的晶体结构引起声子路径弯曲，降低了声子振动的总体频率（<10 THz），并且引起低频光学和声学分支的混合，导致晶格热导率非常低（500 K 时沿x轴和y轴分别为 0.20 和 0.17 W/mK）。单层1T-Ag ₆ S _{2在500 K 时在}x ( y ) 轴上表现出非常高的品质因数ZT为3.14 (3.15) ，明显高于传统TMD 材料。如此优异的热电性能表明单层1T-Ag ₆ S ₂是一种有前途的热电（TE）材料。我们的工作揭示了团簇取代优化材料热电性能的深层机制，为后续研究提供了有益的参考。