Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 10: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 10.11: Talk

Monday, April 1, 2019, 18:30–18:45, H45

Phonon spectrum, phase stability and thermodynamic properties of the cubic pi-phase in the IV-VI monochalcogenides - formation and effect of a phonon band gap — •Uri Argaman, Ran Abutbul, and Guy Makov — Materials Engineering Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.

The pi phase is a recently discovered cubic phase in the IV-VI monochalcogenides with theoretical and technological interest (ref. 1). In this work, the phonon frequencies were calculated ab-initio in the cubic pi-phase of the monochalcogenides in four materials: SnS, SnSe, GeS and GeSe. All four were found to be mechanically stable, and a phonon band gap appears in their spectra. The phonon spectra of all these systems exhibit phonon band gaps in the optical phonon spectrum with widths of 0.7-2 THz. The origin of the phonon band gap was examined through an analysis of the normal modes. The contributions of the geometry of the bonds and mass differences to the phonon spectrum and, in particular, to the band gap are discussed and analyzed. We found differences in the relative motion of the two types of atoms and the rigidity of the bonds in this low symmetry structure. The effect of the phonon band gap on the thermodynamic properties is discussed. In addition, Raman experiment supported the existence of the phonon band gap in pi-SnS and pi-SnSe.

1. Abutbul, R. E., Segev, E., Argaman, U., Makov, G. and Golan, Y. (2018), Monochalcogenide Semiconductors: π*Phase Tin and Germanium Monochalcogenide Semiconductors: An Emerging Materials System. Adv. Mater., 30: 1870310. doi:10.1002/adma.201870310