Results for “AgSnSe2” | Engineering Papers

DOE OSTI2020

Materials Data on AgSnSe2 by Materials Project

AgSnSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ag1+ is bonded to six equivalent Se2- atoms to form AgSe6 octahedra that share corners with six equivalent SnSe6 octahedra, edges with six equivalent AgSe6 octahedra, and edges with six equivalent SnSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Ag–Se bond lengths are 2.85 Å. Sn3+ is bonded to six equivalent Se2- atoms to form SnSe6 octahedra that share corners with six equivalent AgSe6 octahedra, edges with six equivalent AgSe6 octahedra, and edges with six equivalent SnSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Sn–Se bond lengths are 2.89 Å. Se2- is bonded to three equivalent Ag1+ and three equivalent Sn3+ atoms to form a mixture of edge and corner-sharing SeAg3Sn3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Deterministic Control of Sn 3+ Valence and Electronic Phase Evolution in AgSnSe 2

Understanding how unusual oxidation states influence material properties is important for both fundamental science and energy applications. AgSnSe 2 is particularly intriguing because it stabilizes the rare and long-debated Sn 3+ oxidation state, whose true existence and role have remained enigmatic for many years. Here, in this work, we employ X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and X-ray absorption spectroscopy to directly probe the oxidation state of Sn and its evolution under chemical substitution. All experimental evidence consistently confirms the presence of Sn in the +3 oxidation state in AgSnSe 2 . Complementary density functional theory calculations further corroborate this assignment. By substituting Sn with Sb, we systematically control the electronic state and its impact on the material’s physical properties. At low Sb concentrations, AgSnSe 2 retains superconductivity with a transition temperature of ∼5 K, while increasing Sb content deterministically drives a metallic-to-semiconducting transition through progressive suppression of superconductivity. Spectroscopic analyses show that Sb substitution provides deterministic control of the Sn oxidation state, evolving from a uniform +3 configuration in AgSnSe 2 to a mixed +2/+4 valence-skipping regime at higher Sb levels, thereby establishing a direct chemical handle over the material’s electronic phase. This tunability demonstrates that the Sn oxidation state in AgSnSe2 can be precisely engineered through Sb substitution, enabling controlled electronic phase transitions and establishing AgSnSe 2 as a promising platform for quantum and energy-related applications

crystal structure↗