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

Fullerenes with a single lanthanum atom trapped on the inside of the carbon cage were produced by laser vaporization of a lanthanum oxide/graphite composite rod in a flow of argon gas at 1200 °C. When sublimed with C_(60) and C_(70), they formed 
an air-stable film containing principally LaC_(60), LaC_(70), LaC_(74), and LaC_(82). When dissolved in toluene and exposed to air, 
LaC_(82) was found to be uniquely stable. Evidence was also obtained for coalescence reactions between these fullerenes at
high temperatures to form larger cages with as many as three lanthanum atoms inside. Indications have also been obtained 
for the successful production of KC_(60), C_(59)B, and KC_(59)B where the boron has substituted for a carbon in the soccerball cage. 
The use of the @ symbol is advocated for specifying such complex fullerenes as (K@C_(59)B).

Fullerenes with metals inside

Buckminsterfullerene, C{sub 60}, was prepared in gram quantities by contact-arc vaporization of a graphite rod in a 100-Torr atmosphere of helium, followed by extraction of the resultant graphite soot with toluene. The dominance of C{sub 60} in this extract was verified by mass, FTIR, and NMR spectroscopy. The molecule was successfully hydrogenated to C{sub 60}H{sub 36} via a Birch reduction and dehydrogenated back to bare C{sub 60} by treatment with DDQ reagent. Cyclic voltammetry of C{sub 60} in methylene chloride revealed highly reversible formation of at least two stable anionic forms of C{sub 60} in solution. A broad new class of these fulleride and fulleronium ions is anticipated, both with the internal cavity empty and with any one of a large number of elements inside, thus providing a means of fine-tuning the chemical, optical, and redox properties.

Efficient production of C60 (buckminsterfullerene), C60H36, and the solvated buckide ion

Laser vaporization experiments with graphite in a supersonic cluster beam apparatus indicate that the smallest fullerene to form in substantial abundance is C28. Although ab initio quantum chemical calculations predict that this cluster will favor a tetrahedral cage structure, it is electronically open shell. Further calculations reveal that C28 in this structure should behave as a sort of hollow superatom with an effective valence of 4. This tetravalence should be exhibited toward chemical bonding both on the outside and on the inside of the cage. Thus, stable closed-shell derivatives of C28 with large highest occupied molecular orbital—lowest unoccupied molecular orbital gaps should be attainable either by reacting at the four tetrahedral vertices on the outside of the C28 cage to make, for example, C28H4, or by trapping a tetravalent atom inside the cage to make endothedral fullerenes such as Ti@C28. An example of this second, inside route to C28 stabilization is reported here: the laser and carbon-arc production of U@C28.

https://science.sciencemag.org/content/sci/257/5077/1661.full.pdf

Uranium Stabilization of C28: A Tetravalent Fullerene

XPS probes of carbon-caged metals

http://casey.brown.edu/chemistry/research/LSWang/publications/19.pdf

Y. Chai

Papers

Fullerenes with metals inside

Efficient production of C60 (buckminsterfullerene), C60H36, and the solvated buckide ion

Uranium Stabilization of C28: A Tetravalent Fullerene

XPS probes of carbon-caged metals

Fullerene triplet state production and decay: R2PI probes of C60 and C70 in a supersonic beam