### Abstract

A systematic theoretical study on the Si_{n} (n = 26-36, 60) cages using semiempirical methods is herein presented. Equilibrium geometries, harmonic vibrational frequency analyses, enthalpies of formations, HOMO-LUMO energy gaps and other properties are calculated at the level of the AM1 theory. Present theoretical results show that all the Si_{n} (n = 26-36, 60) cage isomers exhibiting maximum symmetry undergo slight distortions into more stable structures of lower symmetry. No simple function for the clusters stability with respect to the number of Si atoms can be discerned in the whole Si_{n} (n = 26-36, 60) series. However, the stability in the Si_{n} (n = 33-36) series decreases as the number of Si atoms drops whereas the Si_{n} (n = 26-32) series shows the same trend with the exception of n = 28 and 31. Several instances of four-fold coordinated, distorted sp^{3} hybridized Si atoms carrying large net charges have been detected. Calculated HOMO-LUMO energy gaps of these Si_{n} cages lie in the range of 3.9-4.6 eV, being larger than those of both smaller Si_{n} clusters and bulk Si. Comparison with available theoretical and experimental data give firm support to the present application of semiempirical methods to large Si_{n} clusters.

Original language | English |
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Pages (from-to) | 47-58 |

Number of pages | 12 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 625 |

Issue number | 1-3 |

DOIs | |

State | Published - May 5 2003 |

### Keywords

- Geometry structure
- HOMO-LUMO gap
- Silicon fullerene cages
- Stability

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## Cite this

*Journal of Molecular Structure: THEOCHEM*,

*625*(1-3), 47-58. https://doi.org/10.1016/S0166-1280(02)00788-1