Rapid shear viscosity calculation by momentum impulse relaxation molecular dynamics

Area of Science:

• Chemical Physics
• Materials Science
• Computational Chemistry

Background:

• Conventional methods for computing fluid viscosity are computationally intensive.
• A novel method, momentum impulse relaxation (MIR), was previously developed for rapid viscosity calculations.
• The MIR method's applicability to larger, more complex systems was previously unexplored.

Purpose of the Study:

• To extend and generalize the momentum impulse relaxation (MIR) method for viscosity computation.
• To investigate the applicability of MIR to larger molecules and systems with higher viscosities.
• To perform a detailed analysis of MIR's performance, including boundary conditions, fitting procedures, preequilibration, and system size effects.

Main Methods:

• Imposition of a Gaussian velocity profile on an equilibrated molecular dynamics system.
• Monitoring the decay of the imposed velocity profile over time.
• Calculating shear viscosity by matching the decay rate to Navier-Stokes solutions.
• Extending the MIR method to multiatom systems and analyzing various influencing factors.

Main Results:

• The MIR method was successfully extended to larger molecules and systems with higher viscosities.
• Detailed analysis confirmed the method's robustness concerning boundary conditions, fitting procedures, and system parameters.
• No loss of accuracy or computational efficiency was observed when applying MIR to multiatom systems.

Conclusions:

• The momentum impulse relaxation (MIR) method is a versatile and efficient technique for calculating fluid viscosity.
• MIR can be reliably applied to complex multiatom systems, offering significant computational advantages.
• This generalization expands the utility of MIR for a broader range of chemical and materials science applications.