Results for “Ag8SnS6” | Engineering Papers

DOE OSTI2020

Materials Data on Ag8SnS6 by Materials Project

Ag8SnS6 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are eight inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to three S2- atoms. There are a spread of Ag–S bond distances ranging from 2.51–2.70 Å. In the second Ag1+ site, Ag1+ is bonded in a distorted linear geometry to two S2- atoms. There are one shorter (2.44 Å) and one longer (2.47 Å) Ag–S bond lengths. In the third Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to three S2- atoms. There are two shorter (2.53 Å) and one longer (2.60 Å) Ag–S bond lengths. In the fourth Ag1+ site, Ag1+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.61–2.90 Å. In the fifth Ag1+ site, Ag1+ is bonded in a 2-coordinate geometry to three S2- atoms. There are a spread of Ag–S bond distances ranging from 2.47–2.95 Å. In the sixth Ag1+ site, Ag1+ is bonded to four S2- atoms to form distorted AgS4 tetrahedra that share corners with two equivalent SnS4 tetrahedra. There are a spread of Ag–S bond distances ranging from 2.67–2.72 Å. In the seventh Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to three S2- atoms. There are a spread of Ag–S bond distances ranging from 2.55–2.68 Å. In the eighth Ag1+ site, Ag1+ is bonded in a 4-coordinate geometry to four S2- atoms. There are a spread of Ag–S bond distances ranging from 2.61–2.93 Å. Sn4+ is bonded to four S2- atoms to form SnS4 tetrahedra that share corners with two equivalent AgS4 tetrahedra. There are a spread of Sn–S bond distances ranging from 2.41–2.43 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to six Ag1+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to five Ag1+ atoms. In the third S2- site, S2- is bonded in a 4-coordinate geometry to three Ag1+ and one Sn4+ atom. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to four Ag1+ and one Sn4+ atom. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to four Ag1+ and one Sn4+ atom. In the sixth S2- site, S2- is bonded in a 5-coordinate geometry to four Ag1+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2021

A Low-Temperature Structural Transition in Canfieldite, Ag 8 SnS 6 , Single Crystals

Canfieldite, Ag 8 SnS 6 , is a semiconducting mineral notable for its high ionic conductivity, photosensitivity, and low thermal conductivity. In this paper, we report the solution growth of large single crystals of Ag 8 SnS 6 of mass up to 1 g from a ternary Ag–Sn–S melt. On cooling from high temperature, Ag 8 SnS 6 undergoes a known cubic ($F\bar{4}3m$) to orthorhombic ($Pna2_1$) phase transition at ≈460 K. By studying the magnetization and thermal expansion between 5–300 K, we discover a second structural transition at ≈120 K. Single crystal X-ray diffraction reveals the low-temperature phase adopts a different orthorhombic structure with space group $Pmn2_1$ ($\textit{a}$ = 7.662 9(5) Å, $\textit{b}$ = 7.539 6(5) Å, $\textit{c}$ = 10.630 0(5) Å, Z = 2 at 90 K) that is isostructural to the room-temperature forms of the related Se-based compounds Ag 8 SnSe 6 and Ag 8 GeSe 6 . The 120 K transition is first-order and has a large thermal hysteresis. On the basis of the magnetization and thermal expansion data, the room-temperature polymorph can be kinetically arrested into a metastable state by rapidly cooling to temperatures below 40 K. We last compare the room- and low-temperature forms of Ag8SnS6 with its argyrodite analogues, Ag 8 TQ 6 ($\textit{T}$ = Si, Ge, Sn; $\textit{Q}$ = S, Se), and identify a trend relating the preferred structures to the unit cell volume, suggesting smaller phase volume favors the $Pna2_1$ arrangement. We support this picture by showing that the transition to the $Pmn2_1$ phase is avoided in Ge alloyed Ag 8 Sn 1–x Ge x S 6 samples as well as in pure Ag 8 GeS 6 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗