Real-space charge distribution of the cobalt ion and its relation with charge and spin states

The charge state of an ion provides a simplified electronic picture of the bonding in compounds, and heuristically explains the basic electronic structure of a system. Despite its usefulness, the physical and chemical definition of a charge state is not a trivial one, and the essential idea of electron transfer is found to be not a realistic explanation. Here, we study the real-space charge distribution of a cobalt ion in its various charge and spin states, and examine the relation between the formal charge/spin states and the static charge distribution. Taking the prototypical cobalt oxides, La/SrCoO₃, and bulk Co metal, we confirm that no prominent static charge transfer exists for different charge states. However, we show that small variations exist in the integrated charges for different charge states, and these are compared to the various spin state cases.