A density functional study of copper hydroxonitrate: size effects and spin density topology

摘要

Copper hydroxonitrate has been investigated within density functional theory and a plane-wave approach. In order to elucidate the topology of the spin density distribution and the microscopic origins of the antiferromagnetic character of this compound, systems with an equal number of unit cells differently oriented in space have been considered. Parallel and antiparallel alignment of spin densities occur between Cu centers, the coupling pattern varying from one plane to the other. Depending on their coordination with the Cu atoms, O atoms carry non-negligible spin densities. These are larger for oxygens on hydroxo groups bridging those Cu atoms which have spin densities aligned in a parallel fashion. The spatial distribution of spindensities is far from being unique, suggesting that the S = O global spin state is compatible with different local spin structures very close in energy.