To make practical the molecular dynamics simulation of large scale reactive chemical systems (1000s of atoms), we developed ReaxFF, a force field for reactive systems. ReaxFF uses a general relationship between bond distance and bond order on one hand and between bond order and bond energy on the other hand that leads to proper dissociation of bonds to separated atoms. Other valence terms present in the force field (angle and torsion) are defined in terms of the same bond orders so that all these terms go to zero smoothly as bonds break. In addition, ReaxFF has Coulomb and Morse (van der Waals) potentials to describe nonbond interactions between all atoms (no exclusions). These nonbond interactions are shielded at short range so that the Coulomb and van der Waals interactions become constant as Rij → 0. We report here the ReaxFF for hydrocarbons. The parameters were derived from quantum chemical calculations on bond dissociation and reactions of small molecules plus heat of formation and geometry data for...

http://www.wag.caltech.edu/publications/sup/pdf/471.pdf

ReaxFF: A Reactive Force Field for Hydrocarbons

THE discovery1 of buckminsterfullerene (C60) and its production in macroscopic quantities2 has stimulated a great deal of research. More recently, attention has turned towards other curved graphitic networks, such as the giant fullerenes (Cn, n > 100)3,4 and carbon nanotubes5–8. A general mechanism has been proposed9 in which the graphitic sheets bend in an attempt to eliminate the highly energetic dangling bonds present at the edge of the growing structure. Here, I report the response of carbon soot particles and tubular graphitic structures to intense electron-beam irradiation in a high-resolution electron microscope; such conditions resemble a high-temperature regime, permitting a degree of structural fluidity. With increased irradiation, there is a gradual reorganization of the initial material into quasi-spherical particles composed of concentric graphitic shells. This lends weight to the nucleation scheme proposed9 for fullerenes, and moreover, suggests that planar graphite may not be the most stable allotrope of carbon in systems of limited size.

Curling and closure of graphitic networks under electron-beam irradiation

Nanochemistry: Synthesis in diminishing dimensions

Although progress has recently been made toward understanding the health and environmental consequences of these materials, challenges ramain for future research.

http://pubs.acs.org/doi/pdf/10.1021/es062726m

Assessing the risks of manufactured nanomaterials.

In this review article we discuss the progress of lithium storage in different carbon forms starting from intercalation in graphite to the lithium storage in fullerenes, nanotubes, diamond and most recently, graphene. The recent advances in lithium storage in various novel morphological variants of carbons prepared by a variety of techniques are also discussed with the most important models in literature that have been set out to explain the excess lithium storage. The major emphasis lies on the real structure.

Lithium Storage in Carbon Nanostructures

The electronic structure of an isolated Ca@C60 molecule was probed by photoelectron spectroscopy (PES) of Ca@C
 60
 −
 , generated by laser desorption of a preformed Ca@C60/fullerene thin film. The PES spectrum of Ca@C60 was found to be similar to that of C
 60
 −
 , except that Ca@C60 has an electron affinity of 3.0 eV, about 0.3 eV higher than that of C60. The spectrum suggests that Ca atom donates its two 4s electrons to the C60
t

 lu
 lowest unoccupied molecular orbital. Thus, the interaction between the central Ca atom and C60 is quite ionic, and Ca@C60 can essentially be expressed as Ca2+@C
 60
 2−
 .

Photoelectron spectroscopy and electronic structure of Ca@C60

Heats of Sublimation from a Polycrystalline Mixture of C60 and C70.

Efficient Production of C60 (Buckminsterfullerene), C60H36, and the Solvated Buckide Ion.

The electronic spectra of supersonically cooled C60 and C70 have been observed in a molecular beam by two‐photon ionization spectroscopy in the regions 375 to 415 nm and 595 to 640 nm. Clear spectral features are observed in both regions for C60 and in the long wavelength region for C70. Neither molecule is responsible for the diffuse interstellar bands.

Y. Chai

Papers

Photoelectron spectroscopy and electronic structure of Ca@C60

Heats of Sublimation from a Polycrystalline Mixture of C60 and C70.

Efficient Production of C60 (Buckminsterfullerene), C60H36, and the Solvated Buckide Ion.

Cold Molecular Beam Electronic Spectrum of C60 and C70.