Improved Local-Mode Zero-Point-Energy Conservation Scheme for Quasiclassical Trajectories

Area of Science:

• Quantum chemistry
• Computational chemistry
• Chemical dynamics

Background:

• The local-pair zero-point-energy (LP-ZPE) scheme is used to approximate zero-point energy in molecular dynamics.
• A known issue is the unphysical leaking of zero-point energy between high- and low-frequency modes.
• This leaking can affect the accuracy of simulation results.

Purpose of the Study:

• To present an improved version of the LP-ZPE scheme, termed the improved LP-ZPE (iLP-ZPE) scheme.
• To address the problem of unphysical zero-point energy leaking in simulations.
• To demonstrate the applicability of the iLP-ZPE scheme in direct dynamics calculations.

Main Methods:

• The study introduces the iLP-ZPE approximation, an enhancement of the original LP-ZPE scheme.
• The method's performance is illustrated through direct dynamics simulations.
• The application focuses on the Ne···HF van der Waals molecule.

Main Results:

• The iLP-ZPE scheme successfully prevents the unphysical transfer of zero-point energy from high-frequency to low-frequency modes.
• Direct dynamics simulations using iLP-ZPE on the Ne···HF system yielded accurate trajectories.
• The method avoids computationally expensive calculations of local Hessians and instantaneous normal modes.

Conclusions:

• The iLP-ZPE scheme offers a significant improvement over previous methods for handling zero-point energy in dynamics.
• It is particularly well-suited for direct dynamics calculations due to its computational efficiency.
• The successful application to Ne···HF validates its utility in studying van der Waals systems.