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An ab initio based global potential energy surface describing CH5+ --> CH3+ + H2
Zhong Jin1, Bastiaan J Braams, Joel M Bowman
1Cherry L. Emerson Center of Scientific Computation, Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
The Journal of Physical Chemistry. A
|January 27, 2006
Summary
A new potential energy surface (PES) for CH(5)(+) accurately describes its dissociation. This ab initio PES, fitted to high-level quantum chemistry calculations, enables accurate dynamics studies of this important ion.
Area of Science:
- Physical Chemistry
- Quantum Chemistry
- Computational Chemistry
Background:
- The CH(5)(+) ion is a key species in interstellar chemistry and plasma physics.
- Understanding its dissociation pathways is crucial for modeling these environments.
- Previous theoretical studies have been limited by the complexity of the potential energy surface.
Purpose of the Study:
- To develop a full-dimensional, ab initio based potential energy surface (PES) for CH(5)(+) capable of describing its dissociation.
- To provide an accurate computational tool for studying the dynamics and properties of CH(5)(+) and its isotopologs.
Main Methods:
- High-level coupled-cluster [CCSD(T)] calculations with an aug-cc-pVTZ basis set were performed to generate electronic energies.
- A permutationally invariant polynomial basis was used to fit the calculated energies, resulting in a PES accurate to 78.1 cm(-1).
- Normal-mode analysis, diffusion Monte Carlo calculations for zero-point energies, and molecular dynamics simulations were employed.
Main Results:
- A highly accurate PES for CH(5)(+) was constructed, fitting 36,173 ab initio data points with a root-mean-square error of 78.1 cm(-1).
- The PES correctly describes dissociation into CH(3)(+) + H(2) fragments and includes equilibrium geometries and vibrational frequencies for these fragments.
- Zero-point energies and dissociation energies (D(0)) for CH(5)(+) and isotopologs were calculated, and molecular dynamics simulations validated the PES for dynamics studies.
Conclusions:
- The developed PES provides a reliable foundation for future theoretical investigations of CH(5)(+) chemistry.
- The accuracy of the PES allows for precise simulations of dissociation dynamics and branching ratios.
- This work advances the understanding of ion-molecule reactions and astrochemistry involving CH(5)(+).