ISSN:
1432-0630
Keywords:
PACS: 61.46+w; 71.20.Tx; 31.15.ct
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
[2+2] cycloaddition reaction between \chem{C_{60}} molecules is studied theoretically using the semi-empirical quantum chemical AM1 method. The studies are aimed at understanding of photo- and pressure polymerization of pristine \chem{C_{60}} and polymerization of the alkali metal (\chem{\chemvar{A}})/\chem{C_{60}} complex, \chem{\chemvar{A}_{1}C_{60}} . Full geometry optimizations of the [2+2] cycloaddition reaction, have been performed for neutral as well as anionic \chem{C_{60}} dimers. Based on these geometries, th e reaction barriers were calculated. Vanishing barriers were found for the anionic dimer and in the first singlet ( \state{}{S}{1} ) and triplet ( \state{}{T}{1} ) excited states of the neutral dimer, results that indicate spontaneous polymerisation for these systems in full agreement with experimental observations. The occurrence of the [2+2] cycloaddition reaction is fully understood from a detailed analysis of the molecular orbitals and how these correlate with the change in the interfullerene distance. We have located a critical intermolecular distance, R_{\text{C}}=\valunit{2.12}{\Angstrom} , for which the [2+2] cycloaddition occurs as a result of an interchange in the position in the energy spectrum between the highest occupied and lowest unoccupied molecular orbitals.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003390050483
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