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Published on: June 28, 2018
Orbital disproportionation and spin crossover as a pseudo Jahn-Teller effect.
P Garcia-Fernandez1, Isaac B Bersuker, James E Boggs
1Institute for Theoretical Chemistry, Chemistry and Biochemistry Department, The University of Texas at Austin, Austin, TX 78712-0165, USA. garciapa@mail.utexas.edu
The Journal of Chemical Physics
|September 27, 2006
Summary
Ground state distortions in molecules with specific electronic configurations can occur due to the pseudo Jahn-Teller effect, leading to spin crossover. This phenomenon involves distinct geometric and spin states with potential for single-molecule switching.
Area of Science:
- Quantum Chemistry
- Molecular Spectroscopy
- Solid-State Physics
Background:
- Systems with half-closed-shell electronic configurations (e(2) and t(3)) typically exhibit high symmetry.
- The Jahn-Teller effect (JTE) is known to cause geometric distortions in degenerate electronic states.
- Spin crossover phenomena are observed in some transition metal compounds, involving changes in spin state and magnetic properties.
Purpose of the Study:
- To investigate the occurrence of ground state distortions in systems with e(2) and t(3) electronic configurations.
- To elucidate the role of the pseudo Jahn-Teller effect (PJTE) in inducing geometric distortions and spin crossover.
- To analyze the electronic and geometric characteristics of the distorted configurations and their implications for spin dynamics.
Main Methods:
- Theoretical analysis of electronic structure and potential energy surfaces.
- Ab initio calculations for various molecular systems (e.g., Si(3), CuF(3), C(60)(3-)).
- Comparison of theoretical predictions with available experimental data.
Main Results:
- Strong PJTE mixing between excited states drives distortions from high-symmetry geometries in e(2) and t(3) systems.
- A novel phenomenon of PJTE-induced spin crossover is observed, linked to orbital disproportionation.
- Distorted and undistorted configurations with different spin states coexist with small energy differences, reducing relaxation rates.
Conclusions:
- PJTE is a key mechanism for inducing geometric distortions and spin crossover in specific electronic configurations.
- The PJTE-induced spin crossover differs from traditional spin crossover by involving distinct nuclear configurations.
- These systems may exhibit single-molecule switching behavior due to reduced relaxation rates, with potential applications in molecular devices.
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