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There are conflicting literature reports related to Fe-Sn intermetallic phases, when, for example, the FeSn2 phase is theoretically predicted to be dynamically unstable due to imaginary phonon modes (see, e.g, C.-J. Yu et al., New J. Chem. 44 (2020) 21218, DOI:10.1039/d0nj04537c). We have, therefore, performed a combined theoretical and experimental study of both FeSn2 and FeSn intermetallics. The theoretical part consists of quantum-mechanical calculations of ground-state properties, including structural and magnetic properties. Computing phonon modes tested the dynamic stability, and the thermodynamic properties were subsequently assessed using quasi-harmonic approximation (QHA). The FeSn2 phase is computed stable, i.e., free of imaginary phonon modes. Importantly, vibrational degrees of freedom significantly affected the finite-temperature stability of FeSn2. We have also characterized Fe-Sn phases using our experimental samples, including X-ray analysis of structural aspects and Moessbauer measurements of magnetic properties. Both the lattice parameters and temperature-dependent Moessbauer factor (see also our previous paper M. Friák et al., Comp. Mater. Sci. 215 (2022) 111780, DOI:10.1016/j.commatsci.2022.111780) turned out to be in excellent agreement with our theoretical results. Financial support received under Project No. 22-05801S from the Czech Science Foundation is gratefully acknowledged. We also gratefully acknowledge the financial support from the Czech Academy of Sciences (the Praemium Academiae of M.F.). Computational resources were provided by the e-INFRA CZ project (ID:90254), supported by the Ministry of Education, Youth and Sports of the Czech Republic. These resources were utilized through IT4Innovations National Supercomputing Center.
