Theoretical study of the stability of the tetradymite-like phases of Sb2S3, Bi2S3, and Sb2Se3

E. Lora Da Silva, J. M. Skelton, P. Rodríguez-Hernández, A Muñoz, M. C. Santos, D. Martínez-García, R. Vilaplana, F. J. Manjón

Research output: Contribution to journalArticlepeer-review

Abstract

We report a comparative theoretical study of the Pnma and R-3m phases of Sb2S3, Bi2S3, and Sb2Se3 close to ambient pressure. Our enthalpy calculations at 0 K show that at ambient pressure the R-3m (tetradymite-like) phase of Sb2Se3 is energetically more stable than the Pnma phase, contrary to what is observed for Sb2S3 and Bi2S3, and irrespective of the exchange-correlation functional employed in the calculations. The result for Sb2Se3 is in contradiction to experiments where all three compounds are usually grown in the Pnma phase. This result is further confirmed by free-energy calculations taking into account the temperature dependence of the unit-cell volumes and phonon frequencies. Lattice dynamics and elastic tensor calculations further show that both Pnma and R-3m phases of Sb2Se3 are dynamically and mechanically stable at zero applied pressure. Since these results suggest that the formation of the R-3m phase for Sb2Se3 should be feasible at close to ambient conditions, we provide a theoretical crystal structure and simulated Raman and infrared spectra to help in its identification. We also discuss the results of the two published works that have claimed to have synthesized tetradymite-like Sb2Se3. Finally, the stability of the R-3m phase across the three group-15 A2X3 sesquichalcogenides is analysed based on their van der Waals gap and X-X in-plane geometry.
Original languageEnglish
JournalJournal of Materials Chemistry C
Publication statusAccepted/In press - 28 Jul 2022

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