The hydrogen tunneling splitting in malonaldehyde: A full-dimensional time-independent quantum mechanical method

Area of Science:

• Quantum chemistry
• Chemical physics
• Computational chemistry

Background:

• Accurate calculation of quantum dynamics is crucial for understanding chemical reactions.
• Ground-state tunneling splitting is a key phenomenon in molecular dynamics.

Purpose of the Study:

• To report the first accurate time-independent quantum dynamics calculations for malonaldehyde's ground-state tunneling splitting in full dimensionality.
• To develop and apply an efficient computational method for this purpose.

Main Methods:

• Developed an efficient method utilizing customized basis functions for hydrogen transfer.
• Reduced Hamiltonian matrix size and employed the Lanczos method with a parallel strategy.
• Overcame memory and CPU time limitations in quantum dynamics simulations.

Main Results:

• Achieved a ground-state tunneling splitting of 24.5 cm⁻¹ for malonaldehyde.
• Obtained excellent agreement with the benchmark value (23.8 cm⁻¹).
• Estimated uncertainty in the calculated value to be less than 0.5 cm⁻¹.

Conclusions:

• The developed method provides accurate and efficient calculations for full-dimensional quantum dynamics.
• The study reveals the significant role of specific vibrational modes in the hydrogen transfer process.
• This work sets a new standard for computational accuracy in tunneling splitting calculations.