Theoretical prediction of Jahn-Teller distortions and orbital ordering in Cs2CuCl2Br2

TL;DR

This paper uses density functional calculations to predict Jahn-Teller distortions and orbital ordering in Cs2CuCl2Br2, challenging experimental structural observations and providing insights into magnetic interactions.

Contribution

It offers a theoretical prediction of the crystal structure and magnetic ordering in Cs2CuCl2Br2, highlighting distortions and exchange interactions not yet confirmed experimentally.

Findings

Predicted elongated CuCl4Br2 octahedra in the ab-plane

Suggested ferromagnetic order of spins in the ab-plane

Indicated small and uncertain exchange interaction along c-axis

Abstract

With the use of the density function calculations we show that the actual crystal structure of Cs$_2$CuCl$_2$Br$_2$ should contain elongated in the $ab-$plane CuCl$_4$Br$_2$ octahedra, in contrast to the experimentally observed compression in $c-$direction. We also predict that the spins on Cu$^{2+}$ ions should be ferromagnetically ordered in $ab-$plane, while the exchange interaction along $c-$direction is small and its sign is uncertain.