Related Experiment Videos
Electron correlation in C(4N+2) carbon rings: aromatic versus dimerized structures
1Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Physical Review Letters
|September 6, 2000
Summary
Large carbon rings show competing electronic effects, leading to structural changes. Quantum Monte Carlo results reveal a crossover from bond angle to bond length alternation around C10-C14, with the second-order Jahn-Teller effect driving the instability.
Area of Science:
- Theoretical Chemistry
- Materials Science
- Condensed Matter Physics
Background:
- The electronic structure of carbon rings (C(4N+2)) is influenced by Huckel aromaticity, second-order Jahn-Teller (SOJT) distortions, and Peierls instabilities.
- These competing effects dictate the ground state geometry, which can be aromatic, bond angle alternated, or bond length alternated.
Purpose of the Study:
- To investigate the ground state structures and electronic properties of large C(4N+2) carbon rings.
- To identify the crossover point and mechanism driving structural transitions in these systems.
Main Methods:
- Utilizing highly accurate quantum Monte Carlo (QMC) calculations.
- Analyzing the interplay of Huckel aromaticity, SOJT effect, and Peierls instability.
Main Results:
- A crossover from bond angle alternation to bond length alternation occurs between C10 and C14 rings.
- The aromatic isomer is consistently found to be a transition state, not a ground state.
- The second-order Jahn-Teller (SOJT) effect is identified as the primary mechanism for opening the electronic gap.
Conclusions:
- The electronic and structural properties of large carbon rings are governed by a complex interplay of many-body effects.
- The SOJT effect plays a crucial role in the structural instabilities, merging with the Peierls regime at large ring sizes.