Zero-Point Energy Leakage in Quantum Thermal Bath Molecular Dynamics Simulations

Area of Science:

• Computational Chemistry
• Molecular Dynamics
• Quantum Effects Simulation

Background:

• Quantum thermal bath (QTB) offers an efficient alternative to path-integral methods for nuclear quantum effects in molecular dynamics.
• QTB provides accurate results for many systems but is susceptible to zero-point energy leakage (ZPEL) in anharmonic systems.
• ZPEL arises from energy transfer between high and low-frequency modes, leading to incorrect energy distribution and impacting system properties.

Purpose of the Study:

• To investigate the conditions and parameters influencing ZPEL in the QTB method.
• To analyze the consequences of ZPEL on structural and vibrational properties.
• To identify strategies for mitigating ZPEL in QTB simulations.

Main Methods:

• Testing the QTB method on systems with progressively increasing complexity.
• Systematic variation of the damping coefficient to assess its impact on ZPEL.
• Analysis of structural, vibrational, and dynamical properties to evaluate ZPEL effects.

Main Results:

• ZPEL is highly dependent on the damping coefficient; increasing its value effectively reduces or eliminates leakage.
• Sufficiently high damping coefficients ensure correct energy distribution among vibrational modes.
• QTB simulations with optimized damping coefficients yield accurate structural properties.

Conclusions:

• The QTB method, when employing a sufficiently large damping coefficient, provides accurate structural properties and is a promising approach for nuclear quantum effects.
• While dynamical properties require cautious interpretation, valuable insights can still be gained from the vibrational spectrum.
• Optimizing the damping coefficient is crucial for mitigating ZPEL and ensuring the reliability of QTB simulations.