Capturing the nuclear quantum effects in molecular dynamics for lattice thermal conductivity calculations: Using ice...

Area of Science:

• Computational Physics
• Materials Science
• Quantum Mechanics

Background:

• Molecular dynamics (MD) is crucial for thermal conductivity calculations in disordered solids.
• Classical MD struggles with nuclear quantum effects (NQEs), leading to inaccuracies for light materials at low temperatures.
• Reliable methods for incorporating NQEs into MD thermal conductivity simulations are lacking.

Purpose of the Study:

• To investigate and analyze the performance of path-integral-based quantum MD methods.
• To assess the accuracy of these methods for thermal conductivity calculations in ordered ice.
• To compare quantum MD results with lattice dynamics (LD) in classical and quantum limits.

Main Methods:

• Utilized path-integral molecular dynamics (PIMD) techniques.
• Employed ordered ice as a test system for simulations.
• Compared PIMD results against lattice dynamics calculations for validation.

Main Results:

• Ring polymer MD shows promise for solids with short phonon lifetimes but faces challenges with long-living acoustic phonons.
• The standard rigid water model inadequately captures NQEs in ice thermal conductivity.
• Ignoring librational and translational NQEs introduces significant errors in thermal conductivity predictions.

Conclusions:

• Accurate thermal conductivity calculations for materials like ice necessitate quantum simulation methods that consistently treat all vibrational modes quantum mechanically.
• Path-integral MD methods offer a viable, albeit imperfect, route to include NQEs.
• Further development is needed for robust quantum MD simulations of thermal transport.