Crystal structure, lattice dynamics and superexchange in MAgF3 1D antiferromagnets (M = K, Rb, Cs) and a Rb3Ag2F7 Ruddlesden–Popper phase

Abstract

With the use of lattice dynamics calculation within the hybrid HSE06 framework we were able to understand the vibrational spectra of MAgF3 (M = K, Rb, Cs) compounds. A comparative theoretical study uncovered a lack of monotonicity in calculated optical phonons associated with Ag-F stretching modes, which can be explained through an interplay of the Lewis acidity of the M(I) cation and its size. We confirm the tetragonal unit cells of MAgF3 (M = Rb, Cs) at room temperature. We also theoretically predict an orthorhombic RbAgF3 polymorph as a ground state at low temperature. However, we were not able to detect it by means of low-temperature powder X-ray diffractometry (at 80 K) nor low-temperature Raman spectroscopy (at 154 K) due to a number of constraints. We also describe a novel Ruddlesden–Popper phase of Rb3Ag2F7 that can be regarded as a quasi-0D system, where the superexchange coupling constant between the nearest Ag(II) centres reaches an impressive value of −240.2 meV.

Graphical abstract: Crystal structure, lattice dynamics and superexchange in MAgF3 1D antiferromagnets (M = K, Rb, Cs) and a Rb3Ag2F7 Ruddlesden–Popper phase

Supplementary files

Article information

Article type
Paper
Submitted
18 Nov 2021
Accepted
22 Dec 2021
First published
14 Jan 2022

CrystEngComm, 2022, Advance Article

Crystal structure, lattice dynamics and superexchange in MAgF3 1D antiferromagnets (M = K, Rb, Cs) and a Rb3Ag2F7 Ruddlesden–Popper phase

K. Koteras, J. Gawraczyński, G. Tavčar, Z. Mazej and W. Grochala, CrystEngComm, 2022, Advance Article , DOI: 10.1039/D1CE01545A

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