Pressure-induced order–disorder transitions in β-In2S3: an experimental and theoretical study of structural and vibrational properties

• Published in: Physical chemistry chemical physics : PCCP 2021-10, Vol.23 (41), p.23625-23642
• Main Authors: Gallego-Parra, Samuel, Gomis, Óscar, Vilaplana, Rosario, Vanesa Paula Cuenca-Gotor, Martínez-García, Domingo, Rodríguez-Hernández, Plácida, Muñoz, Alfonso, Romero, Aldo, Majumdar, Arnab, Ahuja, Rajeev, Popescu, Catalin, Manjón, Francisco Javier
• Format: Article
• Language: English
• Subjects: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; High temperature; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Phase transitions; Pressure; Spinel; Structural analysis; Topological insulators; Transition metals; Vacancies
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d1cp02969j

This joint experimental and theoretical study of the structural and vibrational properties of β-In2S3 upon compression shows that this tetragonal defect spinel undergoes two reversible pressure-induced order–disorder transitions up to 20 GPa. We propose that the first high-pressure phase above 5.0 GPa has the cubic defect spinel structure of α-In2S3 and the second high-pressure phase (φ-In2S3) above 10.5 GPa has a defect α-NaFeO2-type (R3m) structure. This phase, related to the NaCl structure, has not been previously observed in spinels under compression and is related to both the tetradymite structure of topological insulators and to the defect LiTiO2 phase observed at high pressure in other thiospinels. Structural characterization of the three phases shows that α-In2S3 is softer than β-In2S3 while φ-In2S3 is harder than β-In2S3. Vibrational characterization of the three phases is also provided, and their Raman-active modes are tentatively assigned. Our work shows that the metastable α phase of In2S3 can be accessed not only by high temperature or varying composition, but also by high pressure. On top of that, the pressure-induced β–α–φ sequence of phase transitions evidences that β-In2S3, a B2IIIX3V compound with an intriguing structure typical of AIIB2IIIX4VI compounds (intermediate between thiospinels and ordered-vacancy compounds) undergoes: (i) a first phase transition at ambient pressure to a disordered spinel-type structure (α-In2S3), isostructural with those found at high pressure and high temperature in other B2IIIX3V compounds; and (ii) a second phase transition to the defect α-NaFeO2-type structure (φ-In2S3), a distorted NaCl-type structure that is related to the defect NaCl phase found at high pressure in AIIB2IIIX4VI ordered-vacancy compounds and to the defect LiTiO2-type phase found at high pressure in AIIB2IIIX4VI thiospinels. This result shows that In2S3 (with its intrinsic vacancies) has a similar pressure behaviour to thiospinels and ordered-vacancy compounds of the AIIB2IIIX4VI family, making β-In2S3 the union link between such families of compounds and showing that group-13 thiospinels have more in common with ordered-vacancy compounds than with oxospinels and thiospinels with transition metals.