Interplay between electronic and nuclear charge in the photoionization of x@C₆₀ with x = Cu⁺, Cu, Cu^–, Zn

A computational study of the photoionization of atomic outer s and d subshells of endofullerene molecules, such as, the neutral Cu@C₆₀ and Zn@C₆₀ and the ionic Cu⁺@C₆₀ and Cu^–@C₆₀ is carried out. The ground states of the systems are described by density functional theory (DFT) with C₆₀ positive ion-core modeled in a jellium frame. The photoionization is calculated in a linear-response time-dependent DFT framework [1]. The LB94 exchange-correlation functional [2] is employed. Ground state and ionization properties of the outer 4s state are found qualitatively similar among Cu@C₆₀, Cu^–@C₆₀ and Zn@C₆₀. However, for the inner 3d state, even though the properties are found similar within each pair of [Cu@C₆₀, Cu^–@C₆₀] and [Cu⁺@C₆₀, Zn@C₆₀], they are very different from one pair to another. Thus, for 3d, it appears that the nuclear charge of the central species is playing a role in combination with the electronic charge. [1] J. Choi et al., Phys. Rev. A 95, 023404 (2017); [2] R. van Leeuwen and E. J. Baerends, Phys. Rev. A 49, 2421 (1994).