Relative entropy and atomic structure

Relative entropy, using a hydrogen-like model density as the reference, is studied in atomic systems. We find that both the position and momentum space measures display the shell effects, being similar in behavior to the expectation value, 〈r〉. We also show that the electronic momentum density is closer to the hydrogen-like reference than is the position space density. A connection between relative entropy, and the atomic radius and quantum capacitance, is also discussed.