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Symmetry breaking in the cyclic C(3)C(2)H radical
Benjamin Mintz1, T Daniel Crawford
1Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
Physical Chemistry Chemical Physics : PCCP
|October 28, 2010
Summary
We investigated symmetry-breaking in the c-C(3)C(2)H radical using advanced computational methods. Our findings reveal a symmetry-broken C(s) global minimum, driven by a pseudo-Jahn-Teller interaction.
Area of Science:
- Quantum Chemistry
- Theoretical Chemistry
- Computational Spectroscopy
Background:
- The electronic structure of radicals is crucial for understanding chemical reactions.
- Symmetry-breaking phenomena can significantly alter molecular geometries and properties.
- The c-C(3)C(2)H radical presents a case study for exploring these effects.
Purpose of the Study:
- To investigate the potential for symmetry-breaking in the ground state of the c-C(3)C(2)H radical.
- To determine the minimum-energy geometry and understand the underlying electronic interactions.
- To assess the reliability of different computational methods for studying such systems.
Main Methods:
- High-level coupled cluster methods, including connected triple excitations.
- Spin-restricted open-shell Hartree-Fock (ROHF) and spin-unrestricted Hartree-Fock (UHF) calculations.
- Brueckner orbital calculations and equation-of-motion coupled cluster (EOM-CC) methods.
- Analysis of orbital instability and excited-state computations.
Main Results:
- ROHF calculations predicted a C(2v) symmetric structure.
- UHF and Brueckner orbitals indicated a symmetry-broken C(s) minimum-energy geometry.
- EOM-CC yielded a C(s) structure with a double-zeta basis set, but not with a triple-zeta basis set.
- The UHF reference wave function was found to be more reliable than ROHF.
Conclusions:
- The Born-Oppenheimer potential surface for c-C(3)C(2)H exhibits a symmetry-broken C(s) global minimum.
- A second-order (pseudo) Jahn-Teller interaction is responsible for the observed symmetry-breaking.
- This study highlights the importance of selecting appropriate computational references for accurate electronic structure determination.
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