Thermodynamic and thermoelectric properties of the canfieldite, Ag8SnS6, in the quasi-harmonic approximation Joana Cecibel Bustamante Pineda 1 and Janine George 1 1 Federal Institute for Materials, Research and Testing, Department Materials Chemistry, Unter den Eichen 87, 12205 Berlin, Germany, 2 Friedrich Schiller University Jena, Institute of Condensed Matter Theory and Solid-State Optics, Max-Wien-Platy 1, 07743 Jena, Germany. e-mail: joana.bustamante@bam.de, janine.george@bam.de Argyrodite-type materials have lately sparked a lot of research interest due to their thermoelectric properties. [1,2] One promising candidate is canfieldite (Ag 8 SnS 6 ), which has a Pna 2 1 orthorhombic crystal structure at room temperature (RT). Recently, a new low-temperature (LT) phase transition of canfieldite at 120K has been found. [3] Here, we investigate structural, vibrational and thermodynamic properties of Ag 8 SnS 6 at room- and low- temperature employing density-functional theory (DFT) and lattice dynamics computations. Thermal properties calculations were based on the quasi-harmonic approximation (QHA) as implemented in phonopy . We achieve good agreement with experiments. Thermal properties such as the constant-pressure heat capacity ( Cp ) are very close to experimental measurements. Our simulations also reveal a possible new phase transition at around 312 K. Furthermore, we compared RT and LT Ag 8 SnS 6 Grüneisen parameters and group velocities with argyrodites analogues, Ag 8 TQ 6 ( T = Si, Ge, Ti and Sn; Q = S, Se), to arrive at an improved understanding of the low thermal conductivity in these materials. References 1. X. Shen, Y. Xia, C. Yang, Z. Zhang, S. Li, Y.-H. Tung, A. Benton, X. Zhang, X. Lu, G. Wang, J. He, X. Zhou, Adv. Funct. Mater. 2020 , 30 . 2. S. Lin, W. Li, Y. Pei, Mater. Today 2021 , 48 , 198–213. 3. T. J. Slade, V. Gvozdetskyi, J. M. Wilde, A. Kreyssig, E. Gati, L.-L. Wang, Y. Mudryk, R. A. Ribeiro, V. K. Pecharsky, J. V. Zaikina, S. L. Bud’ko, P. C. Canfield, Inorg. Chem. 2021 , 60 , 19345–19355.
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