Theoretical Studies on Structures and Properties of Endohedral Fullerenes Complexes: XH_n@C_(32)(X=F, O, N, C; n=1―4)

Theoretical studies on structures and properties of endohedral fullerene complexes formed by encapsulating small molecules of HF, H20, NH3, and CH4 in a C32 fullerene cage, were carried out by ab initio method. Current calculations reveal that these processes to encase them in fullerene are energetically unfavorable because of the small cavity size of C32. The red shift in the F-H stretching frequency indicates the potential existence of hydrogen bonding between the HF molecule and the carbon cage.

ScY@C_(3v)(8)-C_(82):Metal-Metalσ^(2)Bond in Mixed Rare-Earth Di-metallofullerenes

Comprehensive Summary The experimental investigation of rare-earth metal-metal bonds remains a challenge in the study of chemical bonds.Herein,we report the synthesis and characterization of a novel heteronuclear di-metallofullerene,ScY@C_(3v)(8)-C_(82),which contains a mixed rare-earth metal-metal bond.ScY@C_(3v)(8)-C_(82)was successfully synthesized by arc-discharging method and characterized by mass spectrometry,UV-vis-NIR spectroscopy and single-crystal X-ray diffraction crystallography,which unambiguously determined its molecular structure.Theoretical calculations were also performed to study the optimized positions of Sc-Y metallic dimer and the electronic configuration.The combined experimental and theoretical results confirmed that both Sc and Y atoms transfer two electrons to the C_(3v)(8)-C_(82)cage,i.e.,(ScY)4+@(C_(3v)(8)-C_(82))4-.In particular,a covalent Sc-Yσ2 bond,which has never been reported before,is proven to be formed inside C_(3v)(8)-C_(82)fullerene cage.This work presents a novel di-metallofullerene containing mixed rare-earth metal-metal bond and expands the understanding of metal-metal bonding of rare earth elements.

Path integral Monte Carlo study of(H_2)_n@C_(70)(n = 1, 2, 3)

The path integral Monte Carlo(PIMC) method is employed to study the thermal properties of C70 with one, two,and three H2 molecules confined in the cage, respectively. The interaction energies and vibrationally averaged spatial distributions under different temperatures are calculated to evaluate the stabilities of(H2)n@C70(n = 1, 2, 3). The results show that(H2)2@C70is more stable than H2@C70. The interaction energy slowly changes in a large temperature range,so temperature has little effect on the stability of the system. For H2@C70and(H2)2@C70, the interaction energies keep negative; however, when three H2 molecules are in the cage, the interaction energy rapidly increases to a positive value.This implies that at most two H2 molecules can be trapped by C70. With an increase of temperature, the peak of the spatial distribution gradually shifts away from the center of the cage, but the maximum distance from the center of H2 molecule to the cage center is much smaller than the average radius of C70.

Persistent currents of ultrarelativistic plasma-encased endofullerene molecules entrapping a H atom

In this work,for the first time in the relevant literature,the persistent currents(PC)and induced magnetic fields(IMF)of an endofullerene molecule entrapping a hydrogen atom,under spherical confinement,are investigated.The endofullerene molecule is enclosed within a spherical region and embedded in a plasma environment.The plasma environment is depicted with the more general exponential cosine screened Coulomb potential,and its relevant effects are analyzed by considering plasma screening parameters.The relevant model for endohedral confinement is the Woods-Saxon confinement potential,which is compatible with experimental data.The effects of various forms of Cn are thoroughly elucidated via the analysis of the confinement depth,spherical shell thickness,the inner radius,and the smoothing parameters.To find the bound states in the spherically confined endofullerene,the decoupling of the second-order Dirac equation for the large and small components of the radial atomic wave functions is considered.The Dirac equation with the interaction potential is solved numerically by using the Runge-Kutta-Fehlberg method via the decoupling formalism.The influence of spin orientations on the PC and IMF is also elucidated.The effects of spherical confinement,plasma shielding,and the structural properties of the fullerene on the PC and IMF are thoroughly viewed.Moreover,under given physical conditions,the optimal ranges of these effects are determined.

Atomically Precise Insights into Metal–Metal Bonds Using Comparable Endo-Units of Sc_(2) and Sc_(2)C_(2)

The precise identification of metal-metal bonds is critical to fully understanding the nature of metal-metal bonding but remains a fundamental challenge.Herein,we show the essence of Sc-Sc bonds with a metal-metal distance of 3.36 Å in a C_(3v)(8)-C_(82) fullerene cage using crystallography.

Geometric and Electronic Properties of Metallofullerene Fe@C60

The generalized gradient approximation （GGA） based on density functional theory （DFT） was used to analyze the structural and electronic properties of Fe@C60 and C59Fe for comparison. Among the six possible optimized geometries of Fe@C60, the most favorable endohedral site of Fe atom is under the center of a hexagon ring, i.e., Fe@C60-6. The Energy gap （Eg） of Fe@C60-6 is smaller than those of C59Fe and C60, indicating the higher chemical reactivity. The magnetic moment of Fe atom in Fe@C60-6 is preserved to some extent though there is the hybridization between the ge atom and C atoms of the cage, in contrast to the completely quenched magnetic moment of the Fe atom in C59Fe.

Surface geometry and magnetism of Eu@C_(60) monolayer on Ag(111)

The surface geometry, electronic structure, and magnetism of Eu@C60 monolayer absorbed on Ag(111) have been investigated within the framework of density functional theory. The Eu@C60 monolayer has been constructed on Ag(111) substrate by one of the hexagon faces of C60 downward and its mirror plane face parallel to Ag(111). The Eu@C60 monolayer induces a recon- struction of the Ag(111) substrate and the perpendicular distance between the Eu@C60 and Ag(111) surface is 2.06 A, being shorter than that between C60 and Ag(lll) surface by 0.05A. There is no chemical bond formed between the Eu@C60 and Ag(111), and only 0.55e transferred from Ag(111) to Eu@C60. A large magnetic moment about 6.80/μB per unit cell is found for Eu@C60/Ag(111) system.