IN2ZRBR6 - A VAN VLECK-TYPE PARAMAGNETISM BY INDIRECT COUPLING

Tetragonal In2ZrBr6, a slightly distorted variant of the K2PtCl6 structure type, contains almost cubotachedral InB1211- units that are sharing trigonal faces with ZrBr62- complex anions. In2ZrBr6 is a weak van Vleck-type paramagnet, and we propose that this behavior originates from an indirect electronic coupling between occupied bands with strong indium 5s character and unoccupied, fairly localized zirconium 4d crystal orbitals, moderated by bridging Br- anions. In+ is weakly and nondirectionally bonded to coordinating Br- (there is an almost insignificant indium 5p bonding contribution) and the crystal potential around In+ turns out to be very soft because of antibonding In+-Br- interactions within the highest occupied bands.