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Hydrogen molecules inside fullerene C70: quantum dynamics, energetics, maximum occupancy, and comparison with C60
Francesco Sebastianelli1, Minzhong Xu, Zlatko Bacić
1Department of Chemistry, New York University, New York, New York 10003, USA.
Journal of the American Chemical Society
|June 30, 2010
Summary
This study reveals that endohedral fullerene complexes can stabilize at most two hydrogen (H(2)) molecules in C(70) and one in C(60). Quantum mechanical calculations highlight the crucial role of translation-rotation zero-point energies in determining stability.
Area of Science:
- Physical Chemistry
- Materials Science
- Quantum Mechanics
Background:
- Endohedral fullerene complexes with encapsulated hydrogen molecules (H(2)) are of recent interest for their unique properties.
- Understanding the dynamic and energetic behavior of confined H(2) is crucial for predicting complex stability.
Purpose of the Study:
- To theoretically investigate the coupled translational and rotational dynamics of para-hydrogen (p-H(2)) molecules within C(70) and C(60) fullerenes.
- To determine the energetic stability and maximum H(2) content for these endohedral complexes.
Main Methods:
- Rigorous theoretical study employing Diffusion Monte Carlo (DMC) calculations.
- Calculations focused on ground-state properties, energetics, and translation-rotation (T-R) zero-point energies (ZPEs).
- Analysis of intermolecular potential energy surfaces (PES) for encapsulated p-H(2) molecules.
Main Results:
- Energetically stable complexes are predicted for up to two p-H(2) in C(70) and one p-H(2) in C(60).
- The third p-H(2) in C(70) and the second p-H(2) in C(60) lead to significant energetic destabilization.
- Translation-rotation zero-point energies (T-R ZPEs) are substantial, significantly impacting the overall energetics and stability predictions.
Conclusions:
- At most two H(2) molecules can be stabilized in C(70), and only one in C(60), consistent with recent experimental findings.
- Accurate calculation of T-R ZPEs is essential for reliable theoretical predictions of endohedral fullerene complex stability.
- The findings provide critical insights into the quantum mechanical behavior of nanoconfined hydrogen molecules.
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