Accurate molecular dynamics and nuclear quantum effects at low cost by multiple steps in real and imaginary time:...

Area of Science:

• Computational chemistry
• Quantum mechanics
• Atomistic simulations

Background:

• Accurate electronic structure calculations are crucial for atomistic simulations.
• Treating light nuclei classically is a significant approximation in many simulations.
• Current methods for modeling nuclear quantum effects are computationally expensive, especially with advanced electronic structure theories.

Purpose of the Study:

• To develop a computationally efficient method for modeling nuclear quantum effects.
• To enable the use of high levels of electronic structure theory in simulations involving quantum nuclei.
• To reduce the prohibitive computational cost associated with quantum nuclear simulations.

Main Methods:

• Combining multiple time step integrators with ring-polymer contraction techniques.
• Implementing multiple time stepping in imaginary time to model nuclear quantum effects.
• Applying the method to MP2 (Møller–Plesset perturbation theory) and semi-local DFT (density functional theory) calculations.

Main Results:

• The proposed method reduces the computational overhead of modeling nuclear quantum effects to near zero.
• Inter-atomic forces are described at high levels of electronic structure theory.
• Demonstrated feasibility using the Zundel cation as a test case.

Conclusions:

• The developed approach significantly lowers the computational barrier for quantum nuclear simulations.
• This method allows for the seamless integration with other cost-reducing techniques for path integral calculations.
• Enables more accurate and feasible atomistic simulations incorporating nuclear quantum mechanical behavior.