Simulations of shocked methane including self-consistent semiclassical quantum nuclear effects

Area of Science:

• Computational physics
• Materials science
• Quantum mechanics

Background:

• Atomistic simulations are crucial for understanding materials under extreme conditions.
• Classical molecular dynamics often neglects quantum nuclear effects, limiting accuracy for certain phenomena.
• Existing methods for shock compression may not fully capture quantum thermal properties.

Purpose of the Study:

• To develop a novel computational methodology for atomistic simulations of shock-compressed materials.
• To incorporate quantum nuclear effects dynamically within shock simulation frameworks.
• To investigate the impact of quantum thermal effects on material behavior under shock compression.

Main Methods:

• Modification of the multiscale shock technique (MSST) by coupling it to a quantum thermal bath.
• Implementation of a colored noise Langevin thermostat for quantum thermal bath description.
• Development of the Quantum Bath-MSST (QB-MSST) approach, integrating quantum heat capacities and Bose-Einstein vibrational distributions.
• Application of the ReaxFF potential for atomistic simulations of shock-compressed methane.

Main Results:

• QB-MSST achieves comparable computational cost to MSST.
• The method self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions.
• Simulations of shock-compressed methane show predicted Hugoniot curves comparable to experimental data.
• The onset of chemistry under shock compression occurs at 40% lower pressure compared to classical molecular dynamics.

Conclusions:

• QB-MSST accurately simulates shock-compressed materials, including quantum nuclear effects.
• Quantum heat capacity significantly influences the pressure at which chemical reactions initiate under shock.
• This methodology provides a more accurate understanding of material behavior at extreme conditions.