Xinwei Zhang

Strong metal-cage hybridization in endohedral La@C82, Y@C82 and Sc@C82

Abstract Stimulated by the recent resonant photoelectron spectroscopy studies on La@C 82 who found a nonzero charge density localized on the La atom, local density functional calculations have been performed on La@C 82 , Y@C 82 and Sc@C 82 . In contrast to previous charge transfer model for La@C 82 , Y@C 82 and d-electron localization model for Sc@C 82 , strong hybridization between the La (Y, Sc) d valence orbitals and the cage orbitals have been found in our calculations. Through hybridization the unpaired electron is primarily delocalized on the cage but the occupied valence orbitals contain significant d character.

Density functional theory studies of beryllium-doped endohedral fullerene Be@C60: on center displacement of beryllium inside the C60 cage

Abstract Structural and electronic properties of endohedral Be@C60 are studied via density functional theory method. The results show that Be occupies the center of the fullerene cage and approximately keeps its atomic electronic configuration. The interaction between the Be atom and the fullerene cage turns out to be repulsive.

Structural and electronic properties of heterofullerene C59P

Single P-doped heterofullerene C59P is investigated via semiempirical and density functional theory calculations. Static geometric optimization shows that structural deformation occurs in the vicinity of the dopant atom and gives rise to P-C bonds significantly larger than the ordinary C-C bonds of the fullerene cage. The HOMO and LUMO lie in the middle of the energy gap of the undoped system. Unlike the HOMOS and LUMOs of C59Si and C59N, which are strongly localized on the dopant site, the C59P HOMO and LUMO are weakly localized on the environment of the dopant site. To a first good approximation the dopant P can be considered in the 1 + charge state.

Structural and electronic properties of endohedral and exohedral complexes of silicon with C60

Stimulated by the recent experiment that has added one silicon atom to C60, endohedral and exohedral complexes of silicon with C60 are investigated via semiempirical and first principles calculations. The ground state of the endohedral complex is the triplet state with the encased Si positioned off center, while the ground state of the exohedral complex is the singlet state with higher stability than the endohedral one. The Hartree–Fock HOMO and LUMO of the endohedral complex and the LUMO of the exohedral complex are localized at the dopant Si site. Both adducts have C2v symmetry and enhanced chemical reactivity.

Structural and electronic properties of endohedral phosphorus fullerene P@C60: an off-centre displacement of P inside the cage

Single P-doped endohedral P@C60 is investigated via semiempirical and first-principles calculations. Unlike the encased N atom, which is situated on the centre of the C60 cage and not covalently bound to the carbon atoms of the fullerene cage, static geometric optimization shows that the encased P atom occupies an off-centre position and is bound to the carbon atoms of the fullerene cage. The electronic ground state of the doped system is the spin quarter state, with spin density distribution significantly compressed by the cage.

Cross-sectional transmission electron microscopic study on carbon nanotubules

Structural features of carbon nanotubules produced by arc-discharge have been investigated by high resolution electron microscopy (HREM) along the cross-sectional direction of tubules. Frequently, nested hollow tubules formed by successive cylindrical graphite sheets are found to be polyhedral or elliptical in cross-section which are perpendicular to the tube-axis. Varied spacing between adjacent tube sheets are observed and edge-type dislocations can be distinguished in some tubules. These abnormal structural features are related to accommodations of various strains taking place simultaneously in tube sheets.

STRUCTURAL AND ELECTRONIC PROPERTIES OF ONE DIMENSIONAL KxC60 CRYSTAL ENCAPSULATED IN CARBON NANOTUBE

The structural and electronic properties of potential one dimensional (1D) superconductor — KxC60 chain encapsulated inside a single-walled carbon nanotube is studied using first principles calculations. The stoichiometry of K to C60 of the 1D KxC60 crystal can reach 9, in contrast to a maximal stoichiometry of 6 found in the K doped bulk fullerides. The K 4s electrons are completely ionized, and fill chiefly the C60-derived bands in a nonrigid way. The density of states at the Fermi level of the encapsulated 1D KxC60 crystal is comparable to that in K doped bulk fullerides.