A long-standing debate on the system containing the actinide element is the extent of localization and participation of the 5f orbitals in chemical bonding across the actinide series. Here, we illuminate that the 5f orbitals have both dual nature in superatomic bonding for protactinium, uranium, neptunium, and plutonium using density functional theory. Electronic structure analysis reveals that the partial 5f electrons are active and could be preferentially excited to 6d shells to satisfy jelliumic bonding of the 18-electron rule (1S 2 1P 6 1D 10 ). In contrast, the extra 5f electrons are more localized for neptunium and plutonium compared with protactinium and uranium, and present antiferromagnetic and ferromagnetic couplings for the spin arrangements between actinide atoms and confined gold clusters, and largely localized at the actinide atom. This work offers not only a new recipe for breeding magnetic superatoms, but also is very promising for the designing of superconducting materials and heavy-fermion systems.For a long time, substantial attention has been focused on systems containing the actinide (An) elements. [1][2][3][4] One of the main reasons is that the 5f orbitals can exhibit localization like the 4f orbitals in the lanthanide series, or delocalization (participation) like the d orbitals in the transition metals, or both in the chemical bonding. In fact, the competition has resulted in multiple complicated ground states and phases in compounds and alloy systems. [5,6] Currently, although the degree of localization of 5f electrons has been recognized as the dominant factor in determining the magnetic and electronic properties of the materials, [7,8] experimental methods for measuring the occupancy of 5f electron are still very unsuccessful though some exceptions exist. Therefore, an equally important task is to explore simplified superatomic models containing actinide elements to understand the origin of their properties and enhanced stability.Currently, there are a number of electron counting rules in cluster science that can be effectively utilized in the design and synthesis of materials. [9][10][11][12][13] Among them, 18-electron rule, which is a conceptual extension to the octet rule by the insertion of a metal element with d valence electrons into the closed shell s 2 p 6 (eight electrons), has been regarded as cornerstone for understanding and explaining the transition-metal (especially for the gold clusters) structural stability and physicochemical properties. [14,15] For example, the icosahedral W/Mo@Au 12 cluster was confirmed by theoretical [16] and experimental [17] works, which stability can be attributed to and the 18-electron rule and the strong relativistic effects. Furthermore, the study of M@Au n (M: metal atom of VIIA-IA group; n = 8-17) clusters have shown that at n = 14, the gold-covered bimetallic cluster can achieve the highest binding energy per atom and gap between highest occupied molecular orbital and lowest unoccupied molecular orbital. [18] Therefore, as an important al...
