Details

Autor(en) / Beteiligte

• Kurzyd owski, Dominik
• Derzsi, Mariana
• Mazej, Zoran
• Grochala, Wojciech

Titel

Crystal, electronic, and magnetic structures of M2AgF4 (M = Na-Cs) phases as viewed from the DFT+U methodDedicated to the memory of prof. Rudolf Hoppe.Electronic supplementary information (ESI) available: Details of the calculations of magnetic coupling constants, mapping the potential surface between HT- and LT-K2AgF4. See DOI: 10.1039/c6dt03125k

Erscheinungsjahr

2016-10

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Theoretical investigations of the magneto-structural correlations of M 2 AgF 4 (M = Na-Cs) compounds show that they adopt two polymorphs, the layered perovskite and post-perovskite structures, which differ greatly in the connectivity of the Ag/F sub-lattice and hence in their magnetic properties. With the use of the DFT+U method, the relative stabilities of various M 2 AgF 4 phases were established and the collective JT effect within the Ag/F sub-lattice of these systems was modelled. Calculations show that for all studied stoichiometries, the preferred scenario of the collective JT effect in the layered perovskite phase corresponds to an antiferrodistortive order of elongated octahedra, which leads to 2D ferromagnetic coupling, in agreement with the experimental findings for the M = Cs, and Rb systems. The layered perovskite phase is found to be progressively destabilized with respect to the post-perovskite structure when moving from Cs to Na, again in agreement with the experimental findings. Our results strongly indicate that the layered polymorph of K 2 AgF 4 should not exhibit a ferrodistortive order of compressed octahedra, which contradicts the previous experimental results. Theoretical analysis of various polymorphic forms of a series of four alkali metal fluoroargentates( ii ), M 2 AgF 4 (M = Na-Cs), helped to establish clear trends of crystal structures and magnetic properties across the alkali metal series.