Ab initio global potential-energy surface for H5(+) --> H3(+) + H2.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Molecular Physics

Background:

• Accurate potential-energy surfaces (PES) are crucial for understanding molecular behavior.
• Previous studies on H5(+) lacked a comprehensive and highly accurate PES.

Purpose of the Study:

• To develop an accurate global potential-energy surface (PES) for the H5(+) molecular ion.
• To characterize stationary points and calculate key energetic properties of H5(+) and related isotopologues.

Main Methods:

• Ab initio electronic structure calculations using CCSD(T)/aug-cc-pVTZ.
• Development of a global PES incorporating full permutational symmetry.
• Quantum diffusion Monte Carlo (QDMC) calculations for zero-point and dissociation energies.
• Analysis of isotopic variants like H4D+.

Main Results:

• A highly accurate global PES for H5(+) was generated from over 100,000 ab initio energies.
• Ten known stationary points were characterized and validated.
• Zero-point energy and anharmonic dissociation energy (D0) for H5(+) --> H3(+) + H2 were computed.
• Branching ratios for H4D+ reactions were investigated using classical and quantum approaches.

Conclusions:

• The developed PES provides a reliable foundation for future theoretical studies of H5(+) and its reactions.
• Quantum effects, particularly zero-point energy, are significant and influence reaction dynamics.
• A method for incorporating long-range interactions was proposed.