Investigation of the properties of fullerences by means of molecular dynamics. Ph.D. Thesis
A molecular dynamics (MD) simulation program was developed to model the plastic crystal phase transition of fullerenes. The system considered consisted of 32 C60 molecules. These molecules were represented by rigid, slightly irregular, truncated-icosahedrons. The program used a Lennard-Jones potential and a Coulomb potential for the interaction between the molecules. To allow for structural changes, a variable box was used, as described in the work of the Parrenillo and Rahman. Periodic boundaries and the minimum image convention were applied to the box. A predictor-corrector method developed by Beeman to have a good energy conservation was used to advance the particles. Using this model, the transition points were obtained around 90K and 250K. These transitions agree with experiments. The effects of increasing and decreasing external pressure with respect to the internal pressure were investigated. As a second part of this project, an effort to include long-range forces was undertaken to improve the results of the simulation. The Ewald summation technique proved to take considerable time and memory to run. Increasing the number of molecules in the system was investigated to minimize the need for long-range forces. An investigation was undertaken to see if the Coulomb forces could be replaced by multipoles at temperatures through the phase transitions. As a corollary to the multipole method, the energies and forces of the multipole method were compared with the direct energy and force calculations. Based off symmetry, C60 produces the strongest energies at the l = 6 and l = 10 poles, especially at l = 10. The charge distribution used here also produces strong energies at l = 6 and l = 10 with a stronger energy at l = 10. These results along with the direct evidence of the successful phase transitions, confirms the appropriateness of the charge distribution.
- Research Organization:
- Catholic Univ. of America, Washington, DC (United States)
- OSTI ID:
- 236796
- Report Number(s):
- N-96-21627; NIPS-96-33373; TRN: 9621627
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: Jan 1994
- Country of Publication:
- United States
- Language:
- English
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