The interaction between the inner atoms/cluster and the outer fullerene cage is the source of various novel properties of endohedral metallofullerenes. Herein, we introduce an adatom-type spin polarization defect on the surface of a typical endohedral stable U2@C60 to predict the associated structure and electronic properties of U2@C61 based on the density functional theory method. We found that defect induces obvious changes in the electronic structure of this metallofullerene. More interestingly, the ground state of U2@C61 is nonet spin in contrast to the septet of U2@C60. Electronic structure analysis shows that the inner U atoms and the C ad-atom on the surface of the cage contribute together to this spin state, which is brought about by a ferromagnetic coupling between the spin of the unpaired electrons of the U atoms and the C ad-atom. This discovery may provide a possible approach to adapt the electronic structure properties of endohedral metallofullerenes.

The absorption peak displays a clear blue-shift on the scale of 95 nm for quantum dots (CdSe)13passivated by OPMe2(CH2)nMe ligands in the ultraviolet-visible (UV-vis) spectra.

The structural properties of the uranium-encapsulated nano-cage U@Au14 are predicted using density functional theory. The presence of the uranium atom makes the Au14 structure more stable than the empty Au14-cage, with a triplet ground electronic state for U@Au14. Analysis of the electronic structure shows that the two frontier single-occupied molecular orbital electrons of U@Au14 mainly originate from the 5f shell of the U atom after charge transfer. Meanwhile, the bonding orbitals and charge population indicate that the designed U@Au14 nano-cage structure is stabilized by ionocovalent interactions. The current findings provide theoretical basis for future syntheses and further study of actinide doped gold nanoclusters, which might subsequently facilitate applications of such structure in radio-labeling, nanodrug carrier and other biomedical applications.

As a representative lanthanide endohedral metallofullerene, Gd@C82 has attracted a widespread attention among theorists and experimentalists ever since its first synthesis. Through comprehensive comparisons and discussions, as well as references to the latest high precision experiments, we evaluated the performance of different computational methods. Our results showed that the appropriate choice of the exchange-correlation functionals is the decisive factor to accurately predict both geometric and electronic structures for Gd@C82. The electronic structure of the ground state and energy gap between the septet ground state and the nonet low-lying state obtained from pure density functional methods, such as PBE and PW91, are in good agreement with current experiment. Unlike pure functionals, the popularly used hybrid functionals in previous studies, such as B3LYP, could infer the qualitative correct ground state only when small basis set for C atoms is employed. Furthermore, we also highlighted that other geometric structures of Gd@C82 with the Gd staying at different positions are either not stable or with higher energies. This work should provide some useful references for various theoretical methodologies in further density functional studies on Gd@C82 and its derivatives in the future.

We investigated the geometric structures, vibrational modes, and electronic structures of models of capped (5, 5) carbon nanotubes (CNTs) with four types of defects, namely, V1, V2, V3, and V4, using density functional theory. We found that the defects cause red shifts of the highest peak in infrared (IR) spectra and the highest peak, radial mode, and breathing mode in Raman spectra. There are two IR-active modes localized at V3 and V4 defects. In contrast, the influence of the defects on the electronic structures is considerably case-dependent, with the case of V2 being very special, involving spin polarization and showing a localized feature. The defects cause energy gap change as large as 0.1 eV. By analyzing the density of states of the capped (5, 5) CNT and its four defective structures, we found that at around À7 eV there is a characteristic peak belonging to the pure CNT that could be useful for defect detections. Our results are helpful for understanding the defect effects on the properties of general single-walled CNTs.

The interaction between gaseous uranium dicarbide and graphite is significant for the safety control and design of Gen-IV nuclear energy system. In this article, the interaction mechanism has been studied using a simplified model of adsorption of two typical UC 2 isomers (linear CUC and symmetric triangular structures) on graphene based on density functional theory calculations. The results reveal strong chemisorption characteristics between the UC 2 and graphene, which is found different from the conventional weak intermolecular interaction. Interestingly, although the CUC structure can induce a double sp 3 -hybridization at the graphene, the most stable adsorption structure is formed by the triangular UC 2 adsorbed at the hollow site of the graphene. Further bonding analysis indicates that the U 5f orbitals of the triangular UC 2 are more active than that in the CUC, providing a larger effective bonding area in the adsorption system. Our calculations are helpful for understanding the role of actinide compounds in adsorption on carbon nanomaterials surface, especially for elucidating the bonding properties of 5f electrons.

Water clusters are known to form through hydrogen bonding. However, this study shows that the formation of small water clusters such as (H2O)n with n = 3 or 4 involves strong electron delocalization. Our first-principles calculations reveal that the electron delocalization originates from both the H and O atomic orbitals and extends to the ring center, enriching the bonding characteristics of water clusters.

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