Anharmonic Lattice Dynamics in Sodium Ion Conductors

Thomas M. Brenner; Manuel Grumet; Paul Till; Maor Asher; Wolfgang G. Zeier; David A. Egger; Omer Yaffe

doi:10.1021/acs.jpclett.2c00904

Anharmonic Lattice Dynamics in Sodium Ion Conductors

Thomas M. Brenner, Manuel Grumet, Paul Till, Maor Asher, Wolfgang G. Zeier, David A. Egger, Omer Yaffe

Department of Molecular Chemistry and Materials Science Perlman

Research output: Contribution to journal › Article › peer-review

14 Citations (Scopus)

Abstract

We employ terahertz-range temperature-dependent Raman spectroscopy and first-principles lattice dynamical calculations to show that the undoped sodium ion conductors Na3PS4 and isostructural Na3PSe4 both exhibit anharmonic lattice dynamics. The anharmonic effects in the compounds involve coupled host lattice–Na+ ion dynamics that drive the tetragonal-to-cubic phase transition in both cases, but with a qualitative difference in the anharmonic character of the transition. Na3PSe4 shows an almost purely displacive character with the soft modes disappearing in the cubic phase as the change in symmetry shifts these modes to the Raman-inactive Brillouin zone boundary. Na3PS4 instead shows an order–disorder character in the cubic phase, with the soft modes persisting through the phase transition and remaining Raman active in the cubic phase, violating Raman selection rules for that phase. Our findings highlight the important role of coupled host lattice–mobile ion dynamics in vibrational instabilities that are coincident with the exceptional conductivity of these Na+ ion conductors.

Original language	English
Pages (from-to)	5938-5945
Number of pages	8
Journal	Journal of Physical Chemistry Letters
Volume	13
Issue number	25
DOIs	https://doi.org/10.1021/acs.jpclett.2c00904
Publication status	Published - 30 Jun 2022

Funding

The authors thank Jürgen Spitaler and Maxim Popov (both Materials Center Leoben) for helpful discussions. O.Y. acknowledges funding from ISF(209/21), the Henry Chanoch Krenter Institute, the Soref New Scientists Start up Fund, Carolito Stiftung, the Abraham & Sonia Rochlin Foundation, E. A. Drake and R. Drake, and the Perlman family. D.A.E. acknowledges funding from the Alexander von Humboldt Foundation within the framework of the Sofja Kovalevskaja Award, endowed by the German Federal Ministry of Education and Research; the Technical University of Munich - Institute for Advanced Study, funded by the German Excellence Initiative and the European Union Seventh Framework Programme under Grant Agreement 291763; the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy (EXC 2089/1-390776260); and the Gauss Centre for Supercomputing e.V. for funding this project by providing computing time through the John von Neumann Institute for Computing on the GCS Supercomputer JUWELS at Jülich Supercomputing Centre. P.T. and W.G.Z. acknowledge the Deutsche Forschungsgemeinschaft under Grant ZE 1010/6-1.

All Science Journal Classification (ASJC) codes

General Materials Science
Physical and Theoretical Chemistry

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title = "Anharmonic Lattice Dynamics in Sodium Ion Conductors",

abstract = "We employ terahertz-range temperature-dependent Raman spectroscopy and first-principles lattice dynamical calculations to show that the undoped sodium ion conductors Na3PS4 and isostructural Na3PSe4 both exhibit anharmonic lattice dynamics. The anharmonic effects in the compounds involve coupled host lattice–Na+ ion dynamics that drive the tetragonal-to-cubic phase transition in both cases, but with a qualitative difference in the anharmonic character of the transition. Na3PSe4 shows an almost purely displacive character with the soft modes disappearing in the cubic phase as the change in symmetry shifts these modes to the Raman-inactive Brillouin zone boundary. Na3PS4 instead shows an order–disorder character in the cubic phase, with the soft modes persisting through the phase transition and remaining Raman active in the cubic phase, violating Raman selection rules for that phase. Our findings highlight the important role of coupled host lattice–mobile ion dynamics in vibrational instabilities that are coincident with the exceptional conductivity of these Na+ ion conductors.",

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AU - Grumet, Manuel

AU - Till, Paul

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AU - Zeier, Wolfgang G.

AU - Egger, David A.

AU - Yaffe, Omer

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Y1 - 2022/6/30

N2 - We employ terahertz-range temperature-dependent Raman spectroscopy and first-principles lattice dynamical calculations to show that the undoped sodium ion conductors Na3PS4 and isostructural Na3PSe4 both exhibit anharmonic lattice dynamics. The anharmonic effects in the compounds involve coupled host lattice–Na+ ion dynamics that drive the tetragonal-to-cubic phase transition in both cases, but with a qualitative difference in the anharmonic character of the transition. Na3PSe4 shows an almost purely displacive character with the soft modes disappearing in the cubic phase as the change in symmetry shifts these modes to the Raman-inactive Brillouin zone boundary. Na3PS4 instead shows an order–disorder character in the cubic phase, with the soft modes persisting through the phase transition and remaining Raman active in the cubic phase, violating Raman selection rules for that phase. Our findings highlight the important role of coupled host lattice–mobile ion dynamics in vibrational instabilities that are coincident with the exceptional conductivity of these Na+ ion conductors.

AB - We employ terahertz-range temperature-dependent Raman spectroscopy and first-principles lattice dynamical calculations to show that the undoped sodium ion conductors Na3PS4 and isostructural Na3PSe4 both exhibit anharmonic lattice dynamics. The anharmonic effects in the compounds involve coupled host lattice–Na+ ion dynamics that drive the tetragonal-to-cubic phase transition in both cases, but with a qualitative difference in the anharmonic character of the transition. Na3PSe4 shows an almost purely displacive character with the soft modes disappearing in the cubic phase as the change in symmetry shifts these modes to the Raman-inactive Brillouin zone boundary. Na3PS4 instead shows an order–disorder character in the cubic phase, with the soft modes persisting through the phase transition and remaining Raman active in the cubic phase, violating Raman selection rules for that phase. Our findings highlight the important role of coupled host lattice–mobile ion dynamics in vibrational instabilities that are coincident with the exceptional conductivity of these Na+ ion conductors.

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Anharmonic Lattice Dynamics in Sodium Ion Conductors

Abstract

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