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Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure. Superalkalis have low ionization energy. Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs. In this paper, the geometry, bonding properties, electronic structure, absorption spectrum, and nonlinear optical (NLO) properties of superalkaline M 3O (M = Li, Na)-doped cyclo[18]carbon were studied by using density functional theory. M 3O and the C18 rings are not coplanar. The C18 ring still exhibits alternating long and short bonds. The charge transfer between M 3O and C18 forms stable [ M 3O]+[C18]− ionic complexes. C18 M 3O (M = Li, Na) shows striking optical nonlinearity, i.e., their first- and second-order hyperpolarizability (β vec and γ ||) increase considerably at λ = 1907 nm and 1460 nm. [ABSTRACT FROM AUTHOR]

Purpose and Methods: A global search for the lowest energy structure of CoB192− clusters was conducted. Results: Its ground state is a quasi-planar structure with the Co atom surrounded by a B8 ring. The central Co atom has an oxidation state of +1 with d8 electron configuration. The wave function analysis showed that the Co–B interaction is not a covalent bond. The bonding strength of peripheral B–B bonds is stronger than that of inner ones. The inner B8 ring bonds with outer boron atoms via σ- and π-type bonds. Conclusion: CoB192− shows remarkable aromatic character. [ABSTRACT FROM AUTHOR]

An optimization strategy combining a global semi-empirical quantum mechanical search and all-electron density functional theory was adopted to determine the lowest energy structures of B19Si and B19C clusters. The planarization of a B20 cluster by Si and C atom substitution was observed. The structural transition was from the double-ring tubular B20 to an almost perfect planar B19Si and a quasi-planar bowl B19C. B19Si possessed a geometry with a central B atom surrounded by a six-membered ring and a 13-atom outer ring. B19C adopted a geometry with a B5C six-membered hole. Both Si and C atoms occupied peripheral positions. The observed planarization may be attributed to sp2 hybridization, changes in the peripheral bonding, and structural mechanics. Some properties, including the HOMO–LUMO gaps, on-site charge on Si and C atoms, and deformed charge distribution, were discussed. [ABSTRACT FROM AUTHOR]

An optimization strategy combining global semi-empirical quantum mechanical search with all-electron density functional theory was adopted to determine the lowest energy structure of (InSb) n clusters with n = 6–10. A new structural growth pattern of the clusters was observed. The lowest energy structures of (InSb) 6 and (InSb) 8 were different from that of previously reported results. Competition existed between core–shell and cage-like structures of (InSb) 8 . The structural transition of (InSb) n clusters occurred at size n = 8–9. For (InSb) 9 and (InSb) 10 clusters, core–shell structure were more energetically favorable than the cage. The corresponding electronic properties were investigated. [ABSTRACT FROM AUTHOR]

Purpose and Methods: A global search for the lowest energy structure of CoB192− clusters was conducted. Results: Its ground state is a quasi-planar structure with the Co atom surrounded by a B8 ring. The central Co atom has an oxidation state of +1 with d8 electron configuration. The wave function analysis showed that the Co–B interaction is not a covalent bond. The bonding strength of peripheral B–B bonds is stronger than that of inner ones. The inner B8 ring bonds with outer boron atoms via σ- and π-type bonds. Conclusion: CoB192− shows remarkable aromatic character. [ABSTRACT FROM AUTHOR]

Abstract: A global search for the lowest energy structure of B20Si−, B20Si0 and B20Si+ clusters is conducted. Structural transitions at different charge states are observed. B20Si− is a 2D planar configuration with no polygonal holes, and Si atom occupies a peripheral position. B20Si+ adopts a 3D tubular shape, and each Si is bonded with four B atoms. But for B20Si0, competition among quasi-planar, tubular and cage like structures is found. These structures differ greatly from that of pure B21− cluster. The structural transition may result from changes in the framework of bonding, sp2 hybridization, and structural mechanics. Some of the clusters’ properties including frontier molecular orbital, on-site charge on Si atom, electron density, and magnetism are also discussed. Graphical abstract: [ABSTRACT FROM AUTHOR]

A global search for the lowest energy structure of Co atom-doped boron clusters (CoB 19 + , CoB 19 , and CoB 19 - clusters) was conducted. The lowest energy structures of them are remarkably different from those of B 20 and CoB 18 - clusters. CoB 19 + clusters have a bowl-shaped geometry, where the Co atom is at the bottom of the bowl and is coordinated with eight B atoms. The CoB 19 cluster presents seven- and eight-membered B rings. The CoB 19 - cluster can be viewed as a structure that evolves from a Co-doped boron plane. The coordination number of CoB 19 and CoB 19 - clusters are 16 and 14, respectively. Several low-lying isomers have quasi-planar structures for the CoB 19 - cluster. Some properties including charge transformation and distribution, HOMO-LUMO gaps, molecular orbital distribution, and stability of neutral CoB 19 are discussed. CoB 19 + and CoB 19 - exhibit magnetism with a net moment of 1.0 and 0.94 μ B because of odd number of electrons., Competing Interests: The authors declare no competing financial interest., (© 2020 The Authors. Published by American Chemical Society.)

An optimization strategy combining a global semi-empirical quantum mechanical search and all-electron density functional theory was adopted to determine the lowest energy structures of B 19 Si and B 19 C clusters. The planarization of a B 20 cluster by Si and C atom substitution was observed. The structural transition was from the double-ring tubular B 20 to an almost perfect planar B 19 Si and a quasi-planar bowl B 19 C. B 19 Si possessed a geometry with a central B atom surrounded by a six-membered ring and a 13-atom outer ring. B 19 C adopted a geometry with a B 5 C six-membered hole. Both Si and C atoms occupied peripheral positions. The observed planarization may be attributed to sp 2 hybridization, changes in the peripheral bonding, and structural mechanics. Some properties, including the HOMO-LUMO gaps, on-site charge on Si and C atoms, and deformed charge distribution, were discussed.

The structures, stabilities and electronic properties of endohedral and exohedral B38 fullerenes with transition metal atoms (M = Sc, Y, Ti, Nb, Fe, Co, Ni) are studied using all-electron density functional theory. M@B38 (M = Sc, Y, Ti) possess endohedral structures as their lowest energy structures, while Nb, Fe, Co and Ni atoms favor the coordination of B38 fullerenes in an exohedral manner. Sizable HOMO-LUMO gaps and high binding energies imply the viability of M@B38 towards experimental realization. The distributions of electron density and frontier orbitals are analyzed in detail. The analysis of vertical ionization potential and vertical electron affinity indicates that M@B38 are good electron acceptors and bad electron donors.