Caged-electron states and split-electron states in the endohedral alkali C₆₀

Abstract

The low-lying electronic states of neutral X@C60 (X = Li, Na, K, Rb) have been computed and analyzed by employing state-of-the-art high level many-electron methods.

Endocircular Li Carbon Rings

“…[23] Encapsulating or accommodating guest atoms by carbon allotropes,l ike fullerenes, [24] graphenes, [25] and carbon nanotubes, [26] are well-accepted ways to extend the range of applicability.W ec oncentrate here on alkali atoms as guest atoms.T here are many investigations on carbon allotropes with alkali guest atoms, [24][25][26][27][28][29][30][31][32] which show that they possess interesting geometrical and electronic structures and have much potential for applications.H ere,w eb riefly mention solar cells, [33,34] superconductive agents, [35,36] and supercapacitors. [37,38] As shown in our previous accurate numerical studies,t he electronic structures of endohedral alkali fullerenes vary with different sizes of carbon cages and different alkali atoms.E ndohedral alkali fullerenes can form chargeseparated (CS) electronic states [28,31,[39][40][41][42] as well as noncharge-separated states like caged-electron (CE) [32] and splitelectron (SE) [43] states.S urprisingly,t ot he best of our knowledge nothing is known on carbon rings encircling ag uest atom like Li or other alkalies.D os uch endocircular systems exist as stable entities and if yes which kind of electronic states do they support?…”

Structure and bonding properties of the platinum-mediated tetrametallic endohedral fullerene La3Pt@C98

“…Group III-B rare earth metals (Sc, Y, and Ln), for example, can be captured in cages to synthesize a wide range of endohedral monometallic fullerenes. [9][10][11][12][13][14][15][16] In addition, group I-A alkali metals (Li, Na, K), 17,18 group II-A alkaline earth metals (Ca, Sr, Ba), [19][20][21] and group IV-B transition metals (Ti, Zr, Hf ) [22][23][24] have been successfully trapped into fullerenes in different forms. Furthermore, multiple metal atoms were entrapped by fullerene cages to form bimetallic [25][26][27][28][29][30][31][32] or trimetallic endohedral fullerenes, [33][34][35][36][37][38] which also brought the possibility of the formation of new types of chemical bonds.…”

“…Group III-B rare earth metals (Sc, Y, and Ln), for example, can be captured in cages to synthesize a wide range of endohedral monometallic fullerenes. 9–16 In addition, group I-A alkali metals (Li, Na, K), 17,18 group II-A alkaline earth metals (Ca, Sr, Ba), 19–21 and group IV-B transition metals (Ti, Zr, Hf) 22–24 have been successfully trapped into fullerenes in different forms.…”

On the Endocircular Li@C16 System

“…It is a well-accepted idea that alkali guest atoms can easily form charge-separated donor-acceptor systems with carbon allotropes (Ohkubo et al, 2012;Wang et al, 2012;Yang et al, 2019a). Recently, our group discovered that carbon allotropes with alkali guest atoms can form non-charge-separated states, like caged-electron states in endohedral fullerenes (Yang et al, 2019b), split-electron states in endohedral fullerenes (Yang and Cederbaum, 2021a), and encircled-electron states in carbon rings (Yang and Cederbaum, 2021b). By electronically exciting an endocircular Li carbon ring system, the interaction between the carbon rings and the Li guest atom can shift from donor-acceptor essentially electrostatic interaction to van der waals interaction and vise versa (Yang and Cederbaum, 2021b).…”